I am having a very hard time adjusting my rear brakes.
I have a lower priced mountain bike.
If I adjust it to where it grabs the rim tightly, it slows my bike down due to the resistance from the brake touching the rim.
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You have V-Brakes. These take some setting up but should work okay.
Once all that is done and working, then you can do your brake arm adjustments.
It can be a bit fiddly, but with patience you can make your brakes better. Perhaps not perfect - sometimes the pads themselves harden with age and need replacing.
Pads do wear down over time. If yours are worn past the printed "wear line" then replace.
The springs can also loose their tension with age too - there are usually 3 different mounting hole options, if you remove the whole brake arm. 2.
You did not give us any really specific description of the problem. Therefore, any tutorial for adjusting V brakes should apply. If it is grabbing on one side, you adjust those small screws at the pivot. One of them is visible in your photograph. Using those you make the calipers to be centered around your rim. Then you just adjust the cable pull using your barrel adjuster (at your brake lever) or even at the cable clamp (at the top of the right caliper).
Those should be the important points for you. Full tutorials and descriptions are widely available.