Is possible to buy BTC using Nigerian naira (or ghanian Cedi)(maybe throug payapal if my bank account dont allow me to buy them) and the convert back them in euro?
Why in earth would someone use fiat to buy bitcoin just to convert it to another fiat? It does not make any sense to me if you wish to pay a client in euro them you do not need bitcoin to do so if your clients not crypto inclined, just open your PayPal, fund it and make your transactions.
If your account is restricted from buying crypto then you need a site that offers p2p; Remitano and Binance is a perfect place for you.
Since OP didn't say, I'm thinking he's trying to get euro from something aside from crypto and is using BTC as a means to get access to EUR since it can be bought via P2P.
OP, I'd like to add that you shouldn't use PayPal as a payment method for P2P trades since PayPal payments can be easily reversed. I know p2p trader on binance that lost quite a handful amount of money due to the fact that PayPal reversed most, if not all of the transactions he made and couldn't get the funds back until after 6 months wait time.