Reduce your speed to a comfortable level before the corner. You can pick up speed as you get more proficient. In other words do your braking before the corner not in it. This is the golden rule of cornering. If not your wheel is more likely to wipe out. Approach the corner from the outside if not obstructed by rocks etc. This will give you maximum visibility of what’s around the corner earliest as you start to turn.
There are three body positions to focus on concurrently:
Firstly as you enter the corner think of yourself as carving the corner with your front wheel. It is the front wheel that does the turn and keeps you on. Also past a very slow speed a bike turns not by you turning the handlebars but by you tilting the bike to the side of the turn and the bike therefore turning.
So for example on a left hand turn with body weight reasonable central to back and crouching off the seat put your weight onto the left side of the handlebar tilting and carving into the ground.
Secondly you need to lower your pedal and foot down on the opposite side of the corner (so in this case of a left turn corner the right foot goes down). Dig the weight down into the ground.
Thirdly shift your bottom over the right hand side of the saddle. Your backside and pedal position balance the weight on the front wheel as you carve round the corner.
As you turn the corner get your knee that faces into the corner out as far as possible (on really tight sharp corners at fast speed you can see riders bringing their foot out to balance themselves).
Practice at different speeds. The tighter the corner the more the bike needs to tilt and you with the bike whilst ensuring you remain with the force on the front wheel. All corners are different and hence a great reason to get out more and spend your life practising on your bike. It is the front wheel that does the work.