Hey, there are a lot of places you can go to. If you like adventure, you can try to go to dhanaulti, kanatal or tehri. The major attractions in mussoorie would be landour, hathipaon, George's everest and the mall road. There are a lot of cute Cafes around in mussoorie and dehradun which are peaceful spots, especially for solo travellers. In dehradun, you can go to gucchupani, shahastradhara, FRI, tapkeshwar mandir, buddha temple, poanta saheb etc.