Grammar expert to test in English on Freelance

Hello, I am a Freelancer in Spanish and I need a Freelancer to help me develop two tests in English on a platform designed for Freelance.
I need an expert in English grammar to develop these two exams.
The test has a time of 40 minutes, there are 40 questions.
I need them to take both exams and get a good score, so I need an expert in English grammar.
Preferably a person who is an expert to get a good score.

Please indicate what experience you have had in this matter.