I found this site like a year ago , as you can read in the screenshot above , you receive a free English grammar as you sign up for a free account in Cambridge English Teacher. The topics that are covered in the grammar course are the following:
• Unit 1: Nouns and pronouns
• Unit 2: Adjectives, conjunctions and prepositions
• Unit 3: Verbs and adverbs
• Unit 4: Present tenses
• Unit 5: Future forms
• Unit 6: Past tenses
• Unit 7: Perfect forms
• Unit 8: The passive
Cambridge English Teacher promises you will be awarded a Certificate of Completion at the end of the course.
Here’s quick video of how the course looks
Unfortunately material and other benefits such as webinars and donwloads are restricted to members who pay an annual membership as indicated in their official introductory video.
You might want to try the free grammar course , get your certificate and consider Cambridge English Teacher