Currently we do not have ETA for Easysocial 3, but we will release alpha/beta version for Easysocial 3, so you can clone your live site to one of the staging site, then you can upgrade to Easysocial 3 from staging site.

I use a custom.css, did I have to redo everything?
I use custom files EasySoiel 2.2.5 in the Template, should I delete them?

This very difficult to confirm with you whether you need to re-do all those custom styling or not, because I am not really sure what customisation work you have done in previously, but it would be best if you can test this on the staging site first before you upgrade Easysocial 3 on your live site.

Hello Arlex,
I will actually make an entire backup of the site and database before updating in a timely manner.
I will then do a complete review.
Best regards.
Eric

Alright Eric, but I think the safely way is do it on the staging site first, in case any happen, it won't affect on your live site, because I believe you also need some time to address those issue if there got any issue with the latest update.