first of all … welcome on board!
Then … answering your question is not so easy, infos you gave aren’t so clear; anyway, you can try reinstalling Ubuntu (Budgie, I suppose ) paying attention on where grub is installed (being a laptop I can imagine you have just one hd, so /dev/sda should be the right choice).
Then, if you’re running win 10, I think that you must (?) disable secure boot from bios; for accessing bios you must hit some key before os starts: depending on your pc it could be F8, F12, Del, F2, … but your pc will tell you what you must do in its very first screen (something like “hit F12 to go in bios management” or “hit F8 to change boot order” …).
Please, before you do anything, be careful and backup your data on windows: in the worst case you’d risk to loose data and windows! (but it isn’t so easy to lose everything).
Let us know your progress.