i also cant use most websites like indded for example says something about an ad blocker and i just cannot use this mac anymore effectivly
As far as websites themselves are concerned that may, in fact, be true 😕
Most websites these days use an encryption method El Capitan's Safari version cannot understand. It's too old.
Two possible options:
- If you can upgrade that Mac to a later macOS version, that will extend its useful life at least a little more. To learn how to do that please read How to download and install macOS - Apple Support.
- Try a different browser. Brave and Firefox are two Safari alternatives worthy of consideration.
https://brave.com
https://www.mozilla.org/en-US/firefox/new/
Just be advised both of them are approaching the end of their lives as well, if they're not there already.
Perhaps one of these options will extend the useful life of your Mac.