currently i'm stagnated at 90kg deadlift. I'm going twice the week to the gym.
My main issue is that the grip is difficult and shortly after that i'm not able to hold the bar.
I'm wearing gloves because after at some point the hand inside skin got so open that on the next train it began to hurt, so that I'm not able to do the workout clean.
Should i focus to do some training for the hand or try it without gloves so that the hands get trained?
Improving the grip will improve your game overall, so it's highly recommended. Some exercises for that could be doing Farmers Carry, Pull-ups hold, and so on.
I think the answer to mixed grip imbalances is to switch which hand is supinated. And once you get to a certain weight you'll need to do either mixed or hook grip, so it's good to learn.
The difference between grips and gloves is that usually because of sweat, looseness or whatever, gloves tend to slip. Grips don't, and at most they'll do a wrinkle which sometimes I feel it improves my grip.
The insides are still protected, with a rugged surface maybe, but still better than barehand.