After his middle school friends abandon him during the first week of high school, a childish, imaginative teen attempts to win them back with over-the-top fantasy scenarios, but when his best friend and love interest give him an ultimatum, he must either abandon his playfulness or be a loner forever.

Hi iceisnice,
This is how I see the logline, based on my understanding of the story:

Confronted by his best friend and the girl he has a crush on, a daydreaming teenager must decide whether to act more maturely or be lonely for the rest of his life.

If the above logline describes your story, then use it as a template and re-write.

I hope this helps

Good Luck