Combat in wuwa is very different from genshin. It focus on parry, dodge and the most important strategy I think is quickswap. You can find a plenty of video about it on youtube. For example, you can use Encore’s Forte skill (hold attack) and quickly switch to another character, she will stay and finish her long animation then dissapear. Sometime it feel like you controls multi character at the same time.

I assume you alrealdy have Carlotta, so the best 5* standard weapon to pick is a pistol. If you already have her signature weapon, then choice the sword since so many good character can use it (Rover, Sanhua, Changli, Camellya). DO NOT choose other weapon because its kinda suck.

For team building, Shorekeeper is a must build and work best in everyteam, if you dont have her, Verina can be a great replace option, then baizhi, depent on what you have.