It sounds like you are using a free spool reel. A fixed spool reel is easier for surfcasting. With them the spool is fixed and does not rotate, the line being wound on by the rotating arm.
With the free spool reel the spool rotates as line is pulled off. When the line slows mainly as the sinker or lure enters the water the spool keeps going and throws off excess line which tangles and is difficult to undo particularly with braid.
Some reels have adjustable weights inside which lessen this, however you still need to slow the run out with your thumb on the spool particularly when about to hit the water, you can then lift it off again as it sinks down at a slower rate.
It is probably worth getting a good reel and rod from a specialist shop. Good luck with the fishing.