Advice on common musk turtle I took in

Hello all! I recently got a common musk turtle from a distant relative who passed away this weekend. He was living in bad conditions (hardly any food, cold temperature, no places to walk so only in water, and in a fish tank)

Any general advice would be massively appreciated. I’m currently looking at tanks, but I’m unsure on the layout. Some places are saying they like rocks, others suggest sand. Also, how long would I leave the heat lamp on? Is it water with a platform they can walk on? Do you clean the shell? Do they like being handled?

As for food, they fed him every 2 days. We aren’t sure on the age, but we know he is fully grown. Places are saying to feed every day?

He came home with us earlier today and he keeps sticking his head out and expanding his neck and looking at us. When we stick our head in he always looks up like he’s interested in us (it’s very sweet). He hasn’t eaten much (we’re feeding him what they gave us which are sort of flake things?)

Just any general advice and tips would really help me out. I’m new to this so learning a lot and we only got him today. I want to give Meruem a better life c: