You could try mounting a 30 or 28t chain wheel instead of the 40t supplied.
Also the 28t large cassette cog is limiting, a cassette swap to a 12-32 or 34t
would help on those uphill slogs.
20" drive wheel gear inches:
40:28 is 27 gear inch
40:32 is 25 gear inch (change cassette)
28:28 is 19 gear inch (change chain ring)
28:32 is 17 gear inch (change both)
DIY under $20 mail order to change either chainring
or cassette. No reason LBS couldn't order and install it.