My bike is a Micargi RD-7 7speed road bike

So i don't really know anything about bikes so thats why i'm here. I need help with my bike with a part that broke. The part where the pedal screws into the crank arm?(i think thats what the part is called), well that part when i was riding came loose cuz i think my friend didnt assemble screw it in right and when i rode it on my mornin ride up a hill i tore the pedal out and then noticed that the inside metal screw in part was completely worn down so i cant even screw in my pedal now. Uhh so i dont know what part i need to replace. do i need a new crank? or crank arm or what? Im not looking for a great part just a replacement thats cheap. And can you explain if i need to to and how to measure for new part the size or anything. I know it has 52 teeth. Thanks for the help

I put up pics hope that helps.

You have 2 basic choices.

There are thread insert systems that might be able to save the crank. It depends on how much material was torn out, and whether the outer surface can be cleaned up and made flat, to accept the flange on the pedal. A decent shop should be able to do the job, or determine that it can't be.

The alternative is to buy and install a new crank arm.

Assuming it can be saved, the decision to save or replace would be based on the relative cost.

Lesson for the future, make a short list of various checks to be done before riding, or every few days. It should take but a minute or less and include a glance to make sure pedals are fully threaded in.

While you're at the shop, if you decide to save the crank, you may want to pick up an extra chainring bolt and a few extra washers. You're missing a bolt.

+1

Next time find a friend who actually knows what they're doing, or buy the bike from an LBS. That way it will be properly assembled. Or better yet, if you're mechanically inclined/interested bicycle maintenance is not that difficult to do yourself. You can learn almost everything you need to know from the following:

https://sheldonbrown.com/
https://www.parktool.com/blog/repair-help

I would take your bike to a shop with a good mechanic and show him your problem. they may tell you that a new crank arm is need or that new threads on the same arm are possible. If the price is reasonable to let them rethread the arm then do it. If there price seem excessively high then buy your own tap thread and do it yourself. The right side is a common right handed thread. Check the threads on the pedal, they may be messed up as well. If the pedal arm is shot then you may be able to find a used one in a bike shop, on ebay. They measure 165mm to 175mm from center where arm bolts on to center of where pedal bolts on. good luck