Guild Wars 2

I have 10/11 compelete achivements and when I finish 11. its reset, and I have again 10/11. As 11. I did Snowball Mayhem participal and it reset after 100% completation!
I want my Festival reward and title.

snowball mayhem doesn’t count for the meta because it’s an ‘infinite’ one

You need ‘Ringing the Right Notes’ to complete the Meta. You can click the Meta task box for a drop-down menu showing all needed Achievements and those you have completed.

Good luck.