Hi everyone ! I need advice on extending my fiancee's visa in Izmir

My fiancee is spanish, and im a turk living in izmir, currently with me. She came to turkey on a tourist 3 month visa.

We are trying to marry, but as you know, marrying is not something you can do in a jiffy. So we need more time for preparations or other stuff. Therefore there is a need to extend her visa in any way possible. So i have come here for advice. What i know is ;

we can extend her visa by getting a tourist residence permit which requires $500/month worth of bank account statement or foreign exchange slip for each month, and my notarized commitment saying that she's going to stay with me. or do the same for long term residence permit,just by showing more money.

i have researched a lot and phoned a lot of places but there are some little details i wasnt able to confirm yet. if you can clarify these for me, i'll be glad :

- what kind of foreign exchange slip do we need ? do we need slips for buying foreign exchange, or selling foreign exchange ? or either is ok ?

- her visa is expiring in a month. if the proceedings for visa application takes longer, or they give us a later rendezvous date for application, will that be a problem ?

- how long does it take for applications to be processed in general, and what's your opinion about police's foreign bureau in konak ?

other than these, of course i'd appreciate any advice you may be willing to impart.

thanks.