My brake cable /housing is slipping away from the lever on the handlebars on my bmx bike... What do i do?

go brakeless!

after all those fixxing ang getting your hands dirty, you'll be stripping it off

Redneck solution - remove the housing so that only the inner cable is remaining. Find a piece of steel that is about the same size as a dime. (You can use a penny or a dime, but it's against the law to tamper with money.) Dill a hole at the centre of the piece of metal.

The hole should about be the same size / diameter as the inner cable. Put the end of your inner cable in the hole of the piece of metal. Add oil to the cable and install your cable housing. Your metal piece should fit snug between the brake lever and the cable housing.

Adjust your brakes and you should be ready to go.

Most bars are the same diameter where the brake levers clamp on. Where they get different is at the stem clamp area. More importantly, make sure you get the right levers for your style of brakes - V-Brakes or cantis.