Hello if I go from one place to another (1-3 sone) and have to change to different Metro-lines or RER-lines on your way. Do I have to pay for each trip with my Navigoo Easy card.
Or do I have a time-limit after scanning the card?
If you're using Paris Metro tickets (Ticket t+) on your Navigo Easy card for RER trains, those tickets are only valid inside zone 1 of the RER system. For example, on the RER A train you could go from Chatelet les Halles to Nation, but you couldn't exit at Vincennes and use the Navigo Easy to get out of the station, since Vincennes is in Zone 2.
(Learn more about the Paris RER train zones here.)
For transfers between Metro and RER inside zone 1, yes, transfers are included for 90 minutes after the first validation of a ticket on a Navigo Easy.
I have heard of issues though where people are debited twice on their Navigo Easy for a trip which should have had the transfer between lines included in their first fare validation. We haven't been able to determine why this happened. My guess is a technical issue on the transit authority's side that didn't recognize / include the transfer on the first fare for some reason.
The odd/confusing thing with Metro to Metro transfers is that the Paris Metro system is all one zone and ignores the RER zone system. There are Metro lines which travel into zones 2 and 3, yet are still covered by a single Metro ticket / Ticket t+ since the Metro system is "all one zone".
For example Metro line 5 travels from central Paris (RER zone 1, Gare de l'Est for example) to Bobigny Pablo Picasso station (in RER zone 3), yet is still covered by a single Metro ticket / single validation of a Navigo Easy.