The housing of my brakes on the handle bars is loose and keeps moving. how do i tighten it so that it stops moving when i apply pressure on it and/or squeeze the brake lever??

Open the bleeder on the caliper, then using a large C clamp, clamp it onto the back of the caliper and the middle of the front pad. Tighten it to force the caliper piston back into the housing. If its really stuck you may need to use a bar on the C lamp handle to give you more leverage to get it moving. If the guides are really rusted try soaking with WD40 to free them up before applying pressure..

What's wrong? Will the Parking brake engage? Or is it not working at all?

At the brake handle end of the cable, on the handle bars, ther may be an adjuster that thread into the brake handle from the end of the black portion of the cable. Thread it all the way in and then turn it 2 full turn back out.
Break the nut loose that the brake cable wire goes through.
Inspect that you do in fact have usable brake pad material on the pads.
Squeeze the caliper by lifting the lever towards the black part of the cablewhile pulling on the cable to keep it tight and tighten nut.

pull back on the forward handle it sounds like the clutch brake is on

Your handle bars are most likely stripped or the mongoose head is stripped or a combination of both. Unscrew the bolt you just tightened and take the handle bars off to inspect the little splined area, if smooth than handle bars need to be replaced. The neck should also have those little lines horizontally this area should not be smooth. You can try to wirebrush the area and out it back together, see if that works or the cheapest thing to replace would be the handle bars. When I was a kid I would pin my handle bars so they would not move cause we did a lot of jumping of our bikes and had a lot of stripped handle bars. Mongoose is a good stem I would lean towards new bars. Good Luck...

I'd be willing to bet that you have gotten silicone on the outside of the bars between the handlebar and the throttle sleeve. But, let's try this first. Loosen the two screws that hold the right handlebar switch halves together. Once you get them loose, slide the throttle assembly and the switch housing towards the end of the handlebars about an 1/8" or so. Not much, just a bit to make sure the end of the handlebar is not rubbing inside the throttle grip at the very end. Tighten the screws and try the throttle now. If it works, tighten the two screws securely and loosen the bolts for the front brake master cylinder and slide it down against the handlebar switch housing so you brake light will work correctly.

If this doesn't work, try loosen the cables just a bit. If they're adjusted too tight, the throttle will stick.

If that doesn't work, you'll have to take the throttle sleeve back off the handlebars. Clean out the inside of the sleeve and the handlebars good. Then apply a thin even coat of white lithium grease to the inside of the throttle sleeve and on the outside of the handlebar. Slide the sleeve uo on the handlebar and work it around to make sure it moves absolutely freely. Then reconnect the cables and reassemble the switch housing. Adjust the cables and make sure the throttle works as it should.

Good Luck
Steve

have your breaks and master cylinder pressure checked. maybe your loosing pressure and the brakes are slipping, if it moves and you let off brake and apply again does it hold the car ? On automatics i Have seen a torque converter malfunction that applies torque to trans which would apply pump pressure to trans wanting to make the car very hard to hold,possibly stalling the car out, Possible but uncommon.

with item going 2mph, stand on foot rails, hold on handles,with one foot try stopping walking belt-look at front roller while doing this-if walking belt slips around frt roller, its the walking belt loose. at each corner there is an adjustment,with proper allen wrench, turn CLOCK WISE one turn EQAULLY on each side!! Then recheck,keep doing this untill it quits slipping-Small moves is best don't crank.
Now on other hand if walking belt Stops with frt roller, its the MTR dr. belt under the hood, to tighten,with 2 9/16th wrenchs, I loosen mtr mount bolt,with one hand apply pressure to mtr, retighten, or have wife apply this pressure with her foot,but don't over tightn-u want to turn belt 1/4-1/2 inch on side. Also check walking lube under walking belt!!

Tighten the clamps at the riser.

grab hold and pull straight up!! itll be tight but just pressured on, theres an mounting screw under there, then just pull back down and on