Can an application for a patent for invention be represented?

Naturally, there are professional agencies, which is what our company does, and there should be such professional agencies everywhere. It depends on your purpose. If you just want a patent certificate, you can write it yourself, provided that you can write it and won't be rejected because of writing problems (writing these documents is also learned). Of course, the written patent claim is likely to be too narrow and easy to be bypassed without infringing your patent; And a good agency will naturally help you expand the scope of protection of your patent, which depends on your purpose!