Saudi said they sighted the new moon, so according to them (and few other countries) you have to fast on the 18.02.2026!
There is another opinion, which is followed by Muslim League in Poland, that according to astronomical calculations Ramadan is supposed to start on Thursday, 19.02. Therefore most mosques in Poland (except 1 in Gdańsk and 1 of 2 in Białystok) are going to start fasting on 19.02., with Taraweeh prayers beginning on the 18.02.
There is a valid difference of opinion, so we advise you to either do your own research in the matter and / or follow your local masjid.