Worst possible place to buy a battery. A complete dice roll. Seller is absolutely immune to the long-term consequences you may suffer as a result of cheap construction or corners cut. Product liability insurance? None. Lawsuit? Not possible. Do some looking around on the web and you will see all manner of horror stories.
Now, can you get a working battery? Yes. Chinese sellers are people working to feed their families just like everyone else in the world. But who is it that is selling good stuff and who is selling crap? Good luck figuring that out with certainty. If you want to buy from AliExpress (and I do and have done so for many years) don't pick a product that is a potential firebomb for your learning experience, and don't spend more money than you are prepared to flush down the toilet unless you or others who are willing to vouch for them have experience with the vendor. I have bought many things on Ali and its a good place to buy things from, so long as you realize you are accepting some added risk and behave accordingly.
If I was going to buy a battery from a Chinese source, I would pick EM3EV, who has a well-established reputation for quality and not one for occasional failures, premature wear-outs and fires. UPPBattery on the other hand has all of those things working against it.
The last thing on an ebike you want to go cheap on is the battery. I know its hard to pay the kind of money a quality battery costs, but there are no free lunches no matter how bad you want there to be.