If you've done the Season 7 missions, you've received the Battle Pass for the current season, but unfortunately I've noticed that it's way too slow and I wondered if you could somehow acquire those 25 levels again, even if the free battle has taken
No, unfortunately not. If you still want 25 levels, you have to buy them for 150 V-Bucks per level. Or wait until the end of the season, and then buy in the shop 10 levels for each of I believe 600 V-bucks. Unfortunately you would have had to decide earlier.