Haha I didn't check... and I wasn't in the mood to play when I usually do so I didn't play as a Quarian. Haha there's always tomorrow x
I think it's a silver one?
I don't care that you can't see their faces haha they're beautiful... they have such lovely figures too. 
Haha I was a level 8 Krogan playing gold... even the small enemies took about 4 hits from the hammer and the big ones kept killing me. I don't like the Krogan haha x
I'll use it on a Phantom when I can find one 
Okay, I see, you're in love with Quarians, I don't blame you. To be fair, other species also have good generic figures. By that I mean they're prett fit. I mean you've seen Miranda, Liara, Aria, Traynor...I find my Femshep pretty hot too. Anyways, Quarians are good starter kits in my opinion.
So you were a level 8 Krogan Warlord on Gold, probably no cyclonic modulator on and crappy weapons... man there was no way you were going to do fine. At your level, with your gear and equipement, that kit was good for bronze, no more. With a level 20 and cyclonic IV, you might have been okay but that's very unlikely. Don't expect to keep up withl experienced gold players on your firt weeks, that's not gonna happen. To be honest, many veterans would still have some trouble keeping up with a level 8 Krolord on Gold.
Krogans are not invicible, they're just tougher than pretty much any kit. The one you talked about, the Warlord, his power mainly comes from 3 things : his shield/health/toughness, his melee damage, is biotic/electric hammer. You were level 8, that means you can't fully take advantage of any of that.
One of many easy ways to play him at level 20 is to pick one of the hammer (biotic is my favorite but they both work). How you spec the tech armor is really up to you but max out everything. Put some rage mod melee damage, pick a shotgun or an assault rifle (preferably a shotgun, you're a Krogan!) that has a good effect on shields and barriers. Slap Omni-Blade V (which you don't have yet), Strenght enhancer III (which you probably don't have yet), cyclonic modulator III or IV (which you probably don't have yet) and Juggernaut Shield V (which you don't have yet).
First thing to do is to find an ennemy you can kill with heavy melee without getting in too much trouble or having your teammates kill him first. Once rage mod is on you get extra-protection and melee damage.You need to learn to use the heavy melee and the hammer. When your hammer is charged, if you use heavy melee, it will throw the biotic or electric hammer. If it's not charged it will still throw a basic hammer, dealing basic heavy melee damage. You can also use the classic heavy melee without using your hammer. For that, all you need to do is to run and use melee while running. Finally you can perform some kind of combo attack which can be great to use on Primes as they can't grab you. Basically, all you have to do is lock on an ennemy and press the light melee button three consecutive times. Some ennemies will die after one or two hits. Some will need more and it goes like this, first hit : heatbutt, second : hammer strike, third : ascending hammer strike. Now if your hammer is charged at the time you start the combo, the third strike will be either biotic or electric hammer. A pretty cool and powerful attack...
The safe strategy is to avoid getting sync-killed which at this point for you pretty much means avoiding ennemies with sync-kill abilities. In time you'll be able to know when to use melee attacks, biotic or electric hammer on Preatorians, Banshees, Phantoms etc. but for now, best not go too wild. On the other hand failing is a good way to learn...Geths are a great faction for melee kits because they can't sync-kill you. You have to be able to gauge how much damage you can do with one charged-hammer attack and try to deliver your attack when you think you're gonna get the kill. You can detonate some powers and incendiary rounds with the biotic or electric hammer which can increase damage drastically.
One big advantage of this kit is that he will regenerate his health and shields on his own, so whenever you get in trouble, feel you're taking too much heat, just retreat, recover and come back fully healed. Try to stay on rage mod as much as possible. Your weapon is also important, you might think : I have a frickin war hammer, what am I gonna do with a puny gun ? Which is right in a way, it's ture that when you've mastered the kit, you can go on rampage without using your weapon much, sometimes you can even forget you had one to begin with... But for now, you'll need your weapon, you can use it to strap ennemies of their shields, barriers, stagger them, incinerate them with incendiary rounds or just weaken them before dealing the final blow with your hammer.
Mastering a kit takes time, and you still have to master the basics of the game before you can do that, which takes even more time. I'm not sure playing with people that are way above your level on difficulties like gold is a good way to progress. Unless you play with a team where everyone is willing to follow your rythm instead of their natural pace (which is really unlikely), you'll probably feel frustrated, that you suck, you'll always be running behind, trying to catch up to them and failing to do so. I remember playing on platinum with a low level N7 , no gear, crappy weapons, no equipement, he kept getting wrecked and rage about it. But let's be serious, how can you expect to do as good as someone who has way more fire power, gear, equipement and that has 500, 1000 or more than 2000 hours of gameplay when you have 15 hours yourself.
Veterans, experienced players can basically kill way more things, way faster, safegard their health more efficiently and make the better of varitous situations. So if you play with oldtimers on Gold, chances are you will develop a tendency to rush and overreach your own abilities, that's not ideal to learn. My advice would be to keep playing on bronze for now, with players roughly on the same level or with people willing to teach you the ropes, give you advices and willing to follow the same rythm. Not saying you should never try gold, silver or even platinum, but basically, you'll be ready to handle silver when you're really comfortable on bronze, gold when you're really comfortable on ilver and so on. So sure, have fun on gold, plat, everything , but right now, the place you'll learn the most is bronze, we all went through the process.