OK... 55kg. (121 lbs.) 4.2 m2 and 5.7 m2 should be OK as you are learning.
It might be good to try to find a shorter mast (probably a 400 cm for the 4.2 and a 420 cm
for the 5.7 m2.
Your 4.65 mast would seem very old and probably very heavy.
Not something a 55 kg. sailor should need to deal with.
The GO 155 will work fine in 10-15 knots of wind.
5.7 m2 for 10 knots..... maybe the 4.2m2 for 15 knots.