Trailer brakes
If your trailer is equipped with a braking system, make sure it conforms to your country's regulations and that it is properly installed and operating correctly.
If your trailer weighs more than the maximum trailer weight without trailer brakes loaded, it needs its own adequate brakes. Read and follow the instructions for the trailer brakes so you'll be able to install, adjust and maintain them properly.
Trailer Brakes
Do not use a trailer with its own brakes unless you are certain that you have properly set up the brake system. This is not a task for amateurs. Use an experienced, competent trailer shop for the setup.