2015 Fiesta ST gear changing problems

[north]

Hi all,
I currently drive a 2015 Fiesta St with 40k miles, I've recently started too have a issue with changing gearing whilst moving every time I drive it.

When I'm at a stand still I have no problems selecting every gear, but for instance if I am doing 40mph and and take it out of gear too drop it down into 3rd I'm unable too get into 3rd and will also be unable too get it back into 4th unless therefore stuck in neutral the only way I have found too get back into a gear is if I start too slow down or give the car a slight rev while pressing the clutch it will then slip back into a gear.

I've been searching around and am unable too find anyone who's had the same issue, so please let me know if you have any ideas on if I need a replacement clutch/gearbox or it could be another problem thanks.