Smart won’t start, despite the new battery.

Hello together, lately I have used public transport and after about 2 months of service I wanted to start the Smart again. However, there was only click noise when starting. I assumed that the battery is all and replaced it with a new one. After that you hear the typical noise when starting the engine again, but still it doesn’t start. I am layman and don’t know me. What can be the cause? Thanks for your hints!