Lets boil this one down to some useful advice for someone who recently started windsurfing.
ONE: get a bigger sail, an 8.0 with two cambers would be quites suitable. It would push down the planing threshold quite substantially
ONE.ONE: Get a bigger fin so that the baord can benefit from the 8 m2 sail, something around 46 cm would be just right.
With a new bigger rig and a longer fin you will be able to learn a lot, and have a lot of fun, with your current Funster 180.
TWO. At a later point in time you can then switch the Funster for a more advanced board, for example a freeride board in the 120-130 liter range.
THREE, Get an additional sail between the 5.5 and the 8 m2, maybe a 6.5.
That is a nice and logical progression.