If you don't like the finished tattoo, and the pattern is not too big and complicated, you can change it, but no matter how good the technology is, it will still leave traces.

Find a regular hospital, and some dermatology and plastic surgery departments can wash it.

If you want to wash your tattoo, don't go to the beauty salon on the street. Basically, you can't wash it off after cheating, and washing tattoos is more painful than making tattoos.