Ok so let's just say I bought BTC on kraken and downloaded it to my wallet. I want to sell it on cionbase. All I need to do is just sent it to my coinbase account. Sorry it might sound stupid asking about it but I'm absolutelly new to this
Yes, you can do it directly.
When you want to withdraw Bitcoin, you go onto Coinbase and check what Bitcoin address they want you to send to. Then you set your withdrawal address on Kraken to that Coinbase address and it should go directly to your Coinbase account, assuming that Kraken is punctual with withdrawals.