To squash the last 10 commits into 1 single commit:
git reset --soft HEAD~10 && git commit -m "squashed commit"
If you also want to update the remote branch with the squashed commit:
git push -f
If your are using the above approach to simplify resolving merge conflicts, then I would rather suggest the following approach:
From your current branch, just do
git pull --rebase origin master
This will rebase your branch against master, and conflicts may come max once(instead of multiple times) since all your commits are put on top of master.