@Erinç1
I am in exactly the same situation, the rear boundary of our property is shared with our High School oval as per this screenshot. The marking indicator only indicates the area not the actual location of our listing. Our listing is one of those that share a rear fence with the oval
I regard the oval as being a plus rather than a negative. If it was a primary school I may think differently but noise from the oval, except for once a year sports days, is almost nonexistent and I guess the only mild annoyance is the hour that it takes the school ground staff to mow the oval grass once a fortnight. They do however generally mow late morning when guests have already left or about to.
School children only use the oval during teaching breaks and for half an hour at lunch time. They are gone by 3.30 pm and the oval is just a quiet peaceful space to run the dog.
With well over 400 guest stays Erinc, nobody has ever complained about the fact that the oval is there, and I do not even make mention of it in my listing description, so from my point of view I would not put it high on my issue list. Concentrate on other purchase criteria like, how convenient is the property for guests, is there shopping within walking distance, is there a busy noisy road nearby, is there convenient guest parking. Are there any noisy businesses in the area.
The oval should be the least of your problems!
Cheers........Rob