Chain belt

[Ramy]

Hi all, I have got a problem with my Nissan Micra K12 , during last couple of months I have noticed that when I switch the engine on , it does not work from first ignition but it works from second time , few days ago I came into the car and started the engine but it fail to start and the engine light came on , but when I tried again , the engine started without issues , after this has happen , I noticed that I became able to start the engine from first time and not from second time as I used, this a bit wierd because I expect that after the light come on the car will get worst or won't be able to start at all but what happen that it became better as I started to be able to start the engine from first time, but the engine light is still on during driving. I used a diagnose of one of my firends and I have received two error codes P0340 which says Camshaft position sensor and P0335 which says Crankshaft position sensor , next to the second code is mentioned ( pending ) , I visited a garage yesterday and they said that they need to put the car on the diagnose reader but they said that it will be most likely the chain belt will need to be changed, I do not know why they said that however the diagnose of my friend did not chow fault related to chain belt , any advise please?