Transmission problem
2004 Vauxhall Corsa 4 cyl Two Wheel Drive Manual 50000 miles

I have a 2004 1.2 corsa about 50000 miles and the gearbox is playing up, it is really haard to put the car into 1st second and mainly reverse gear. The reast of the gears are very smooth but when i try 1st/2nd or reverse with the clutch fully depressed,I have to force it in with great pressure. Please help. Thanks