Question about my first brew...

So I brewed a German Amber Ale kit for my first solo brew. Everything went really well, except for the fact that I brewed during a freak heat wave. Anyways, this was over the summer, and tasting the beer now, it's not bad by a long shot, but I can definitely taste a slight "off" flavor. Reading around on here, I guess I would describe it as an almost banana flavor, but only very slight. During the first day of fermentation, my fermometer read 80+ degrees, but after 24 hours, the rest of the fermentation was at around 74 degrees. Was that first 24 hours at a bit of a higher temperature enough to give that off flavor? I just want to make sure I fix my mistakes for the next brew!

it could just be the yeast you used, but...

yes. during the beginning of fermentation, yeast activity is at it's highest. that means lots of alcohol is being produced as well as flavor.

you are tasting esters. lower temperature should help with that problem.

i always check the 7 day weather forecast before i brew. i never brew when there isn't 7 days of 65 or lower temperature for the next week.

Yeast can get up to a lot of mischief in 24 hours. Definitely sounds like estery flavor to me.