In Medium ticker the season is almost over. Last year I lost my entire transferbudget. Currently I have over 100mln left, but is that amount also being “deleted” after the season tick?

yep

Shall I put this topic in the bugdepartment? I mean, come on, what else can one do with his last 100mln? At least let me buy cute girls or get me into a Rubysoccer casino!!

You get some extra points for it next season.