Try Breezetech https://breezetech.co.uk/
In full disclosure they are a partner of NappyValleyNet but they have had some lovely reviews from users who have tried their services.
In addition they came to us via another happy partner who uses them regularly.
I too had some gmail issues a little while back and it turned out that I had email overload from spam
the spam wasn't at all obvious but it was going on in the background.
Good luck in fixing the situation it is very frustrating!