I have a nissan micra on a p 1.0 cc

Try adjusting the cable a bit and see if it makes a difference. Keep track of how many turns you make on the adjuster so if you need to,you can go back to where it was before you began. Could be a stretched cable or the disc may have worn a bit.If it's not slipping you may still have a few miles left in it. I'm betting that the disc is worn. The gears that are difficult to engage may have worn synchros. A clutch problem will aggravate that.