dont know how to use stones to break limits!

Please help me understand the concept of breaking limits with stones. .i have a magic stone but dont know how to use it!

Mudah saja

انا مش عارف ازاي استخدام الأحجار الكريمة في اللعبة ولزمتها ايه

You have to upgrade an item past a certain level. "Upgrades of up to 100 levels for Legendary equipment, 80 for Epic, 60 for Rare, 40 for Magic and 20 for Normal are possible." The the upgrade button becomes break and you can use your stones to break the limit. Different stones for different types of weapons. More Info: https://game.nanoo.so/darksword/forum/455641?code=5b709c13b17d29f4369768de22e5ed68

And for UNIQUE ? What is the max level ?

So if i have a tier 6 epic +80 and i use a gem on it... will it become a tier 7??

unique is 120 max level

No... you will upgrade +81, +82, +83, ... :-)))))