Broadband, as opposed to narrow band voice service, has always been available in your area, its what you are using currently.
The fibre (fibrenet) service should be an improvement on what you've got at the moment, although be careful the 20meg service is not a fibre service but in fact an ADSL2+ service, rather than your current ADSL service. So if you want the 'real' fibre net service (a fibre service to the road cabinet some where near to your home and then a copper pair of wires (that you currently are using) to your home, then:
(a) you may not be able to get it or perhaps get it but the speeds are not as advertised
or
(b) like the ADSL2 and 2+ service in Turkey the fibrenet services will not give you a guaranteed minimum service as they do in most other countries in the world, and the service could fall well short of the advertised 20,35, 50 and 100 meg services.
But in general you will get an improvement from any step up in service, particularly in the upload speed, but as most people use the service for mainly downstream activities like streaming for TV etc., that advantage may not be so noticable. You just have to balance the risk of the increased price you pay and what service you ACTUALLY get from the fibrenet service (whether it be 20, 35, 50 or 100 meg!!) and you will probably not know that until they install it!!
Be very interested to hear what does happen, if you do go ahead with the upgrade.