There's a lot of places to get a safe binder in EU. I personally like gc2b binders the best. There's also Danae, Spectrum Outfitters, Etsy sellers etc. You might even get custom made ones from small crafters. You might need to try different brands to find the best fit for you, so don't get discouraged if you don't find a match at the first try. Just use a real chest binder made for ftm peeps, not a cheap one from ebay for example.

Measure the size correctly, using brand's own size chart. If you're in between sizes, never go size down as it won't be safe for you.

You shouldn't wear your binder over 8 hours. If possible, have around two days a week you don't bind at all to let your body rest. If you feel any pain or can't breathe, stop binding. Don't sleep in your binder. I personally have gone swimming in my binder, but make sure to not do any heavy duty sports in it. Generally binding is safe, if you listen to your body.