I second the SSD recommendation, a change you will definitely feel.

You can use CPUZ to find what your motherboard is and then look it up and find what is the maximum amount of ram it can accept (probably it will work for laptop, I’m not entirely sure).

As for ram frequency, I believe (but not sure), that you can get higher frequency ram but your pc will only use up to the frequency it supports. So you can buy higher frequency ram but you don’t really want to because you’ll end up paying more for less.

I believe pc components stores and ram manufacturers have tools that identify your hardware and recommend their parts for upgrades, you could try them.