Time Calculations

Good Evening. I am new to this forum. I hope someone can help. i have attached my spreadsheet i have been working on but what i would like to do is not have to enter the colon in when entering the start time and end time.

I do have hidden formulas in the row below what you can see in each square. What I have so far has taken me 3 nights of searching the web but i cant seem to find anything on auto adding the colon with the way i have my sheet set up

thanks in advance for the help