Which route are you thinking of?

www.biroto.eu/en/ has gpx tracks for loads of European cycle route, often as segments or both full route as well as segments, incl Eurovelo routes (and loads of others).

To download routes you have to register (free). Some routes are open license, others copyrighted (download displays license). Not the easiest site to navigate and to find what you are after can take some searching around (e.g. there isn't just the one gpx for a route). But they are just tracks not turn by turn directions.

Also remember that in places some Eurovelo routes have multiple "routes" you can take.

Or I may have misinterpreted the question. If OP is asking about a Eurovelo route already in cycle.travel where they want just part of the route, maybe find or create a "via point" where you want to start and do a "delete before" and via point at end of section and do a "delete after".

Uncertain if "downloaded from the website" means downloaded from cycle.travel or a different website.

Ian

Thank you Richard and Psamathe for your comments. Sorry for taking so long to reply. Cycle.travel has available the EV routes that I wanted. I was so please to find them that I forgot to write and say 'thank you'.