Ford KA unable to change gear

??????????

I have a 2014 Ka.. when driving anything from 10 mins to longer an issue appears where by it gets stuck in gear. Mainly first so for example.pulling off at a roundabout or junction.. the only way to get it out is to switch off and then dip clutch and yank it out and try all over again..on restart the car os very sluggish to start and lacks power it is very intermittent.. the clutch has just been done as we thought it was that but still same issue. Ou done 18000 miles so hoping its not gear box. Any ideas would be gratefully appreciated.

Checked the clutch fluid level , checked clutch master cylinder for any sign of leaks under dash at pedals , tried bleeding ?