German's difficulty is concentrated in noun gender/case and a distinctive word-order system — a roadmap that manages both deliberately from the start avoids having to retrofit them later.
Learn the alphabet (see German Alphabet) quickly, then start vocabulary by always pairing a noun with its article (der, die, das) — never learning a bare noun, since retrofitting gender later is much harder.
Of the four cases, these two cover a large share of basic sentences — treat dative and genitive as later additions rather than a prerequisite to speaking.
Practice simple sentences that don't start with the subject (time expressions, for example) to internalize verb-second order early, rather than only ever practicing the simplest subject-first pattern.
Once basic sentences feel comfortable, tackle separable-prefix verbs (see German Verbs) and practice breaking apart long compound nouns (see German Vocabulary).
Alphabet and basic vocabulary: a few weeks. Comfortable basic conversation with nominative/accusative-heavy sentences: several months. Confident handling of all four cases, verb-second/verb-final distinctions, and separable verbs: a year or more of consistent study.
See also the reference page: Learn German.
Always learning a noun together with its article (der, die, das) from the very first encounter — retrofitting gender onto vocabulary you already "know" is much harder than building it in from day one.
Nominative and accusative — they cover a large share of basic sentences, with dative and genitive worth adding progressively afterward.
Practicing sentences that start with something other than the subject (like a time expression) helps verb-second order feel natural sooner than only practicing simple subject-first sentences.
Basic conversation with nominative/accusative-heavy sentences takes several months of consistent study; confident handling of all four cases and word-order rules typically takes a year or more.