I have a laptop with a system from 15 years ago and therefore it can no longer be connected to the Internet. I don't have any special LAN cables or other things, is there another option or do I need a new system?
You should first agree whether you mean Wi-Fi or Internet.
He can't do both
Which laptop? Which system?
Possibly. Is it also possible with a WLAN USB stick.
Unfortunately, this answer shows that you do not have the necessary know-how to solve this problem - also with the help here.
You need a minimum level of network knowledge that is not available.
So I can advise you to read the http://www.olivergast.de/blog/2011/04/16/netzwerkguide_1/ first.