1984, oh dear ;-)
Marcel, let me start with a few questions:
What boards you used to sail back then? Div2, raceboards, funboards?
What are the wind conditions on your lake (average/gusts, number of days, etc)?
I think it would be best to try a few boards at first, before you buy one. Depending on the wind conditions and how "rusty" you are, you may need a daggerboard (phantom etc) or a shortboard bigger (and wider) than 155 GO.