As someone who can read basic Polish, let me tell you that the English version of the PKP website is both poorly translated and out of date compared to Polish one. Whilst the grammar makes sense, it doesn't say what they mean to say in quite a few places.
If you are traveling a lot and using non PKP trains, the Koleo app is very handy and you can buy tickets on the phone up to a minute before departure. It has an English version but PKP won't allow them to sell tickets for their services, all the other companies are happy to though. It's pointless bothering with the PolRegio app since it's just a skinned version of Koleo restricted to PR trains only.
For on the move live running information, and looking up trains, I'd recommend either the new Portal Pasażera app, or an old version of Bilkom. The PP app is more modern, a few nice features and generally works well although I still find the old version of Bilkom a little more accurate and a bit easier to use.
Oh and don't bother with the PKP IC Mobile Navigator app, it's only in Polish, asks for lots of crazy permissions, prefers payment methods that are obscure outside Poland and needs a Polish phone number to sign up for an account by forcing SMS verification.