>>16516800the school system is just extremely inefficient at teaching languages and the pupils usually lack the interest in actually learning the language, and usually forget it like the maths or whatever else they got taught at school because they don't use it in their daily life (language skills can be forgotten like anything else)
it is better to teach yourself the language or come to germany if you want to learn german
the resemblance with the slavic languages is a comparison i would make, high german is grammatically the second most conservative germanic language and thus shares many similarities with the slavic languages that other germanic languages (besides more isolated ones like icelandic and faroese) don't. it can be found in the genus system, the case system, the conjugation etc. although it is far more similar to english in the end than to czech.