Is killing Kitava impossible for me? Character screwed up? (new player)

I just hit a complete brick wall with my Marauder on Kitava in Act5. The fight itself seems rather easy, but it took me about 40 minutes to remove barely 25% of his health, then game disconnected as it regularly does and I just ragequit, because srsly, WTF???

Any advice whats wrong? Or its just a failed char and I have to make a new one?

Thank you in advance.

Is this your lvl 48 marauder? looking at your gem links, you are missing quite a lot of gem. You can use aura gems like hatred, ash of fire, lightning, ice. Your ground slam should have 3 other gems linked to it, eg melee physical, ruthless, maim, multistrike, faster attacks etc. there is also anscestral warchief or ancestral protector that can help you