I have a watch that vibrates rather than bleeps. If I press a button the countdown stops but the count up keeps going and a separate count up of tome added on starts. While paused it vibrates every 10 seconds to remind me to restart it. So I can see how much time is gone, how much remains, of that how much is added on. There are never any dramas.
On my other wrist I have a normal digital watch and I write the start time of each half on my match record card.
Sometimes it helps to indicate that the 'clock is stopped' by ostentatiously having my hand on a button.
To the OP: best of luck. Don't worry too much about timekeeping in your first match. Ask 10 refs and you'll get 11 different ways of doing things. Enjoy yourself.