4 months old puppy

Labradors are easy. Take it outside to where you want it to go in your garden on a regular basis. Rain, snow or sun. Pre-empt it needing to do it inside. Use a command like Go Pee-Pee when outside. Take it outside the moment you wake up. Take it outside when you go to bed. Put it in a cage at night.
Friends have a bell by the back door that their lab rings to go out!!
Ours was virtually accident free.

Go to your local library and get a book out on dog training.

Your mutt. You take responsibility for it.

Contact your local veterinarian/dierenarts and ask them.
Also contact DogID.be Tel. 02 333 92 22 Email info@dogid.be
They are open from 8am to 8pm daily.