Sounds like you need to rebuild your 3-point lift piston,it's not a real hard job iif you are mechanical. If you will send me a pic of your hydraulic lift box (the part under your seat) I can tell you if our rebuild kit will fit it.
Send pic to :
tommy@affordabletractorsalesco.com
Tommy
Affordable Tractor Sales
“Your Jinma Parts Superstore”
http://www.affordabletractorsalesco.com