This could be a couple of things. Firstly I’d try a new battery and see if that resolves it because it seems the problem is electrical – from your description I don’t think there’s anything wrong with the clutch although it’s difficult to tell without actually looking at the car. Could also be the gearbox ECU which is under the battery to the front of the gearbox. I’d say if it’s not either of these, you need to check out the clutch and gear actuator – possibly the clutch actuator has failed although I’m not sure you’d be able to select gears if it had. I’d try the new battery first and go from there – but be aware any estimate you get from a garage is just going to be guesswork at this point as they’ll have to try and test a few things.