Ideally, especially if this is your typical practice, you would remove the gel manicure prior to immersion. In this case, though, where you can’t do that well on your own and the manicure is in good shape, you should fill in and repair your manicure as well as possible, clean your nails very carefully, and immerse. You should check in with your mikveh attendant in advance about this to ensure that mikveh policies will allow for immersion in line with this halachic ruling.