What to fix on an Orbea Carpe 30 2018?
Hi guys, I recently decided to get into cycling after not having owned a bike since I was a small teenager. I bought a cheap-ish used 2018 Orbea Carpe 30 since my plan is to start using it to commute to work/into town and build up my confidence on two wheels. Then if I do catch the cycling bug, I can then spend a bit more money on a new gravel bike before going on longer rides.
The Orbea set me back £150 from fb marketplace. After having taking it on a few test rides now, I found that when you select gears 1 and 2, the cogs don't change and stay on the lowest gear (1) (the indicator changes though). When you select gear 3 then the cog changes into the 2nd lowest gear. Basically, the gear indicated is of by one and I can't select the highest gear (smallest cog).
Also, when I'm on the highest indicated gear (second smallest cog) and going at speed while trying to pedal, there is jerkiness where it seems like the chain is not fully engaging with the tooth and slips.
My diagnosis, from my very limited experience, is that I will need a new chain and possibly cassette. Can anyone suggest what else it might be or what sort of servicing I can do? I really want to try learning how to do things on my own rather than taking it to a shop although, for more complex jobs, I know I'll need to do that. Appreciate any help!