If I level up on gta 5 ps4 will my progress carry over to PS3?

No, your progress in Grand Theft Auto V on PS4 will not carry over to the PS3. Each platform maintains its own separate save files and online progress, meaning you cannot transfer your level, characters, or any other progress between the two consoles. If you switch from PS4 to PS3, you'll have to start fresh on the older console.