As others have posted, you probably are facing multiple problems.
You have a long way to pump the waste and you're using far too light of wiring through a very limited connection in your car to attempt to power your pump.
1. STOP using your automobile cigarette lighter socket to power your macerator pump. It's going to either burn up your car wiring or burn up the windings in the pump motor.
2. Use the largest diameter hose to connect to the macerator pump. A 3/4" minimum diameter would produce less "pressure against the distance", but you may wind up needing a 1" diameter (even though both ends of the hose are 3/4" fittings.
3. ALWAYS run water into the tank as you're pumping the waste out. The more liquid you have, the thinner the "paste in the bottom" will be and the easier the pump can push the LIQUIFIED not pastey material.
4. Buy a quality, heavy duty cigarette lighter extension with alligator clips and connect it to your trailer battery (the trailer power center will recharge the battery if you're connected to shore power).
You can find the type of cigarette lighter extension here: https://www.amazon.com/YCIND-Battery...1zcF9hdGY&th=1
There are cheaper ones that are "lighter duty" for less money, but you need, at a MINIMUM, 12 ga copper wire and a 25AMP rating. This link has three selections, a 3', a 6' and a 10' wire length. Choose according to the distance from your trailer battery to where the connection to the macerator pump is located. There are cheaper devices like this available, but they do not have the wire gauge to provide the amperage you need. DO NOT CHEAP OUT ON WHAT EXTENSION CORD YOU BUY.
DO NOT SKIMP ON WIRE GAUGE. The reason why your pump is overheating and shutting down is because it's not getting enough power to push the waste. That's a combination of "light duty power supply that can't provide the amperage needed and the distance waste is being pushed combined with the thickness of the waste liquid. Increase the extension cord capability, reduce the thickness of the waste liquid. You can't do much about the distance, so use the largest diameter hose as possible.