Malzahar

Hes pretty easy. Whenever the enemy goes to CS, put E on them, and run away and you'll win the trade. Your ult is great. It supresses them so they can't do anything while you're ulting them. If you lie down your W under them while you ult them, you'll lock them ontop of it, dealing a lot of % max hp damage. Your Q can be hard to hit but it deals nice damage, and its not too bad with some practice. You can use your W to kill tanky enemies as it deals % damage based on their max HP, and you can use it to zone them in lane.

Build wise I would reccomend going Rod of Ages > CDR boots and then sitautionally. Void for Magic pen, deatchap if youre snowballing. If your team lacks CC, rylais can be good because the slow lasts a log timewith your E. Liandry's torment is really good because your E refreshes the passive, and you get a lot of burn dmg with it. Between Liandries and your W, you can melt tanks with ease :D

Hope this helps, sory if it was kinda long XD

you can go to mobafire to get more in dept guides/builds but the one already provided is really good

AP right now is here for utility (IMO). Max E first, W second, and jack up your CS. Build your AP hard because your R is used to melt tanks.

You're immobile so take Flash and Ghost. Max your CDR along the way because you want that Ult up as much as possible. You're to backline the team fights and quietly ruin lives.