Badly fitted windows

[Kimmiju]

Hi 

 

I’m new here so apologies if this is in the wrong area. 
I took over a house a year or so back and there are a number of jobs that need doing so I expect I’ll be asking lots of questions here 😂

first… the windows at the front are badly fitted and look botched. Whoever fitted them just filled the inch or so gap at the top with silicone and it’s splitting. 
any advice on the correct/best way to fix this (without replacing the windows) would be greatly appreciated. 
initially I thought that expanding foam might work then silicone or some kind of cover strip. 
It’s obviously letting water in, some days when it rains hard water is running down the inside of the windows. 
 

tia.