Moving PHP code into a Widget

Hello,
I need to help a friend that have a WordPress website developped by someone that stop to work for him.

If i’m familiar with website dev i’m not with WordPress.
Part of the coding have been done directly in the php page where (i believe) it should have been integrated to WP tools.

Part of the side is Widget but some are coded in the sidebar.php file.
Is there a way to cut the relevant code from the .php and to paste it in a Widget ?

I tried text widget bud it didn’t parse.
Before i break anything i’d like to have some feedback.

Thanks