Many Anglo-American holidays or other significant days sooner or later hit the German-speaking countries and find their way into the German language, usually without being translated. Fairly recent examples would be Halloween and Black Friday. Valentine's Day (in German "Valentinstag") is celebrated in Germany since the 1950's. Even though its customs are fairly similar to the UK and USA- buying roses for your loved one and taking them out to a romantic dinner (in non-Covid times, that is)- Valentinstag is generally a more low-key affair in Germany compared to other parts of the (mostly Western) world, and regarded by some as nothing but a commercial day invented to drive sales. Still, you might be curious how to wish Happy Valentine's Day in German. We usually say "alles Liebe zum Valentinstag" (literally, all my love for valentine's day) "alles Gute zum Valentinstag" (all the best for valentine's day).
So there you go. And now pick the flowers!
On our German language blog "Auf Deutsch, bitte!", you will find posts on confusing words like the German noch, false friends like "gift" and the German "also", as well as articles on many grammar topics- from German adjective ending rules, on how to use the four German cases, where to place nicht in a German sentence, an explanation on when to use zu in German sentences, question words in German, and on German word order.