can someone explain me how it is, that for example same company stock on Frankfurt exchange is +50% and on TSX is -10% (same day). Do they have fixed amount of shares on every other exchange?
The percentages are relative to the previous day's closing at each exchange; as the exchanges close at different times, the closing prices are different every day.
The only way to compare them usefully is to look at the absolute prices at both exchanges at the same point in time (while they are both open). The difference should then be minuscule, and if you are fast enough, you might be able to make a tiny bit of money (buy on one, sell on the other); that is called 'arbitrage trading'.