Just explain to them what happened, I doubt they will fire you.

I’ve heard great things about cleaning windows with windex and newspaper.

It’s too petty to fret over. The streaks are proof that you tried. I suspect that whatever towel or cloth you used is responsible.

It depends on how big a dick the bank manager is and how much of a wimp your boss is as to whether you get fired or not. I’d think not. But I’m with @cheebdragon on the use of newspaper. That was an old trick I learned in the navy. If you want the best results, go over the windows once as you currently are then do a final wipe with a dry newspaper.

You did your best. The sun hitting anything you clean at the right/wrong angle and intensity will show everything. If they let you go over it then accept that it is not the kind of place you want to work for.

If you get fired for trying your best for an hour but not having been trained to get better results yet, then you’re probably better off not working for that company.

I have to second all of the sentiments above. You did your best and a few streaks on a piece of glass is not the end of the cosmos. If they fire you over something that petty, move on. Screw those people and the jackass they rode in on.

You always seem to be worried about losing your job for small things like this.

Well if I make enough small mistakes then I could get fired.

Try to describe the situation to your boss so that he knows in advance what you were doing, I’m sure he will understand you, but for the future you should do your job more responsibly by distributing the forces and stages of your cleaning in advance