Latin, of course, is the root of all Romance languages and in many other European languages, Latin remains a significant contribution. But Latin has practically no use in our time. If you think about base language, then from a practical point of view, Spanish seems to be better suited. About 700 million people speak it, that is, it is very useful in itself, and it is much closer to the modern languages of the Romance group than Latin.
As for German, it is unlikely that it can be a useful basis for learning even the languages of northern Europe, German is very different from any neighboring languages. Undoubtedly, German itself is useful, given the enormous economic influence of German-speaking countries. Learning German is also useful as a challenge - German grammar is probably the most difficult among European languages.