How am I supposed to act?

Hello people! And this is about the following problem: My car battery seems to be mucking a little bit lately. What can I notice? Well, sometimes the car doesn’t start immediately. After the 2 or 3 times it starts again and it works. But in the long run, it can’t go on like this. I wanted to ask, how would you act? I have read that a charger CAN help, how do I know if it will work or not? Can you have it checked somewhere without vi You always want to save money .. And if I have to buy a new battery or just a charger, does your online or specialist store mean? I mean by now you can probably also buy this through Amazon, Ebay etc.. Do you think it’s worth it or rather “old-fashioned” in the store? Thank you in advance!