Would installing make the computer faster?

I have two laptops, an old one and another that’s about 2-3-years-old. They are for my father. We bought the second one because the old one was slow, now they are both slow (the second one is functional but slow)

My father uses word and facebook (he writes and shares his righting a lot) and a bit of youtube, that’s all he knows how to do

To solve the slowness problem I thought to install ubuntu. So I tried installing it on the old laptop. I chose the option of removing windows completely, and I managed to install it with no problem (it does give me an error when I install apps, something like '/data/' folder does not exist).

But it’s still extremely slow, I tried to open libereoffic and it just takes ages to load.

This is on the first old computer

Is it me, have I installed it wrong, is it the computer?

I’m scared to do the same thing to the second laptop as it would mean I would have to re-install windows and so on and I hate doing this (especially when it’s not for myself)

Do you have any tips?

I chose to remove windows instead of running parallel because I should it would give ubuntu more breathing room, would it be a good idea to install ubuntu on the second laptop in parallel or …

(I later found that I should have checked whether my laptop is 32-bit or 64-bit, I didn’t, is there a way to do it now and reinstall ubuntu again, or could it definitely be the laptop’s fault for being too old)

(sorry for not being technical enough)