The sentence with afspreken I would translate in English as 'shall we meet up some time' (I don't know the exact meaning of 'verabreden', but I think it is the right translation).
'Meiner Meinung nach' sounds rather official to me - the Dutch sentence says 'I think / I believe I have fallen in love with you'.
Es war nett mit dir gewesen zu sein maybe? (I have had a good time with you.)