Need Advice How To Delete Activity Log From A Group I Am Admin For

[tammyshep1950]

Need advice how to delete activity log on a public group I am admin for. I run a lost stolen found site on Facebook and lately I am having to vet all the posts as some disgusting photos are trying to post on my site. I have deleted and blocked loads but now I would like to delete them from the groups activity log. When I click on the 3 dots of each post it doesn’t give me the option to delete. Your help would be very much appreciated

[THECORBYLOON]

Would it not be an idea to contact Facebook directly for advice?