Login redirect to current page

I don’t know if this is in the correct forum.

I’ve tried many options for this including a plugin, adding things to functions.php, modyfying wp-login.php and am getting nowhere. I have now wasted about 10 hours trying this so please can somebody help.

I want to use the default admin bar “login” button but have it stay on the same page after login. Has anyone got this working?

Is it possible just by adding things to functions.php?
Is it possible just by editing wp-login.php or do other things override this such as byddypress?
Is it possible just by adding bp_custom.php?

Which option to use? Do they all work?
If wp-login.php is an option, which part of it to edit, there’s so many references to $redirect_to

Please can somebody help. It’s driving me mental. So much wasted time on something that should be done by default yet to get it to work in WP seems like a nightmare.

Thanks for any help.