Upgrade laptop but how?

I have a laptop that is very slow but I don't know how to get it faster. Can someone help me?

This is difficult or even impossible with a laptop. The effort is often not worth it, so a new laptop is usually the best idea.

If there's no SSD yet, one could be retrofitted.

You would have to know what equipment it already has. But in general you can say that the laptop will probably be faster by swapping the hard drive for an SSD or possibly a little more RAM. Otherwise there's actually nothing that can be done with a laptop.