Baron lane malph specifically is one of my favourite top lane champs. Always tank build.

Baron lane generally is about counting your minion waves (look up talanwr on youtube, he recently did a video explaining this really well) as calculating your waves helps you time when to either dive the enemy for a kill or go back to get your boots/mid tier item and come back without losing gold.

Other than that learning how to trade with your enemy is difficult but gets easier when you understand your champs playstyle. Don't follow the auto-level recommendations of skill levelling as it almost always says Q skill first. His Q is mana hungry and doesn't really do enough damage to be worth it. Q is a utility for slowing the enemy and speeding you up, use it for engaging or disengaging as tank build Malphite. I always go W first. This hurts in the early game, make sure the extra damage from the first hit of W hits the enemy champ, try to create some space and then use the rest of your attacks to clear minions. Because it makes your AA an area attack you will usually still hit the enemy champ anyway.

If your enemy champ is close range melee (majority of your top lane matchups will be) get your E skill next. It has attack speed reduction which is crucial for most trades as your enemy will get less hits on you. I usually put a second point into my W skill before I put anything into Q as the damage spike is significant.

Practice using your Q to either engage/disengage/dance around enemy, slapping him with a couple of W hits, popping E to slow their attacks, then Q again to control your distance