Based on all your evidence, you can have different strategies. According to the time node of evidence, it is mainly divided into three aspects:
1, you have conclusive evidence to prove that the technology has been publicly used before the application date. The so-called public use does not mean that everyone knows it, but that the technology has been used before the application date. In this case, his patent does not pose a threat to you, but you lose the opportunity to apply for a patent. Of course, you can declare his patent invalid.
You can enjoy the right of first use if you have conclusive evidence to prove that you have made all preparations for using the technology before the application date. That is to say, according to Item 2 of Article 69 1 of the Patent Law, if the same product has been manufactured, the same method has been used or the necessary preparations have been made for its manufacture and use before the patent application date, and it continues to be manufactured and used only within the original scope, it will not be regarded as infringement of the patent right.
All your evidence can prove that the time node is after the application date, then he can prohibit you from using the technology.
You can consider:
1. Both parties negotiate to change the patentee and add or change you as the patentee.
2. Bring a lawsuit against unfair competition.
3. The patent application is invalid. If it is not authorized, you can put forward the opinion that the patent application cannot be granted to China National Intellectual Property Administration.
Specific analysis of the specific situation.