After erasing 200 GB I need to repair it using the Recovery HD I was cleaning my MacBook Pro, erasing all unused files I had on it. After that I decided to erase the free space, so I will have all my files organized and cleaned the "used space". After that I verified the disk that shows the following error:


  This disk needs to be repaired using the Recovery HD. Restart your computer, holding down the Command key and the R key until you see the Apple logo. When the OS X Utilities window appears, choose Disk Utility.


The questions are:


My mac will go from scratch, means erase all the programs, files, music, pictures etc?
What if I install Yosemite, will it solve my problems?
If number 2 doesn't solve the problem, are there any steps I should take now?


I'm now backing up my MacBook on time machine, just in "case" I lose it all, and before I erased the free space all was fine!
No your Mac will not reset all you files. It is just maintenance of file system and not your files.
No it will probably not solve your problems. It even can make matters worse on filesystem level. Or just ask you to do the same i.e. Repair Partition.
You should just do what it you are asked — boot to Recovery HD with CMD + R on startup and Repair Main Partition.


Word of caution: It might be that you HDD is failing so do Time Machine backup or other form of backup before going futher.