MOUSE BUG

Well i was starting to play after installing ... then i notice that the mouse was not working i was clicking on the mouse like usually i used too , to walk and nothing happend , i did try to find a solution , i did go to the options , then hotkeys , then "player moviment" was somenthing wrong ... the mouse dont fix ... only like a example : shift click , fn click .... but that is really confusing for me because i used to walk only with the mouse ... i dont know how to fix it ... and im not playing until i fix .... PLEASE HELP ME I ALREADY CRY BECAUSE OF THAT.** is really frustating ... cause i can't play decently ;c**