I bought a house about a month ago, and one thing that I noticed after trying to install a valance in the kitchen was a rush of hot air coming in from outside. Above the window there was a gap that you could see straight outside through.

On the inside of the window there was a thin strip of something that had 2 screws holding it up, and it was coming down on the right side where the air was coming in. As it was 1am and I just wanted the 90 degree heat to stop, I pried up the strip back into place, screwed it in like it was in 2 other places to the left, and then sealed the top. (2nd picture)

Outside there's the same issue, except no strip of anything that is attempting to fix the issue. (first picture)

Do I need to have an entirely new window installed that I guess is taller so it fits? I can't see any gaps to the left or right of this area, it's just the top of the window isn't tall enough to go all the way to the piece that's above it. Is there something I can buy and screw in on the outside and seal the edges?

Here are the pictures of what I'm talking about. https://imgur.com/a/AdN7umC