Understandably it depends on frequency of practise
But,
How long does it take (has it taken) to be able to play
most of the basic notes on the trumpet?

How long has it taken to be able to play `ad-lib`?

play ad-lib, like improvise?

Yep

I know somebody who still can`t play decently from sheet music, but he`s a fantastic player when it comes to improv, so that heavily depends.

You have to play long enough to have a relationship with the instrument. Also, play all the music you can, play new instruments, sight read, play anything. Immerse yourself in music, listen to good music (improvised or not) and play along. Learn melodies and try adding embellishments where ever you can. I only practice about 20 minutes a day, you could go for longer, but make sure you work up to it gradually. If you overpractice, you won`t be able to play well at all, so work up to whatever you do. Also, try working on ensembles. Have a few friends in band play with you, on a melody that everyone knows and try playing a decent rendition without music. Also, sing, it helps to be able to sing harmony. Hope this helps,

Bonnie

for the notes it takes a few months to play them like 1 0r 2 but it takes a while to play them with tone