Celtic Heroes

Ive played this game before on data (year or 2 ago) n had no problems with selling or fighting. Now im on wifi (nothing else lags) and rarely like 2 or 3 times a day i will be selling fish or items to an npc n it lags so bad i have to restart the game entirely. Also when im on the dock in lirs reach ill open the menu to go to my skills etc n exit out n the dock is completely gone out from under me n i cant move