Germans speak in Perfekt — this is THE everyday past tense.

Use sein with verbs that express motion from A to B (gehen → ist gegangen, kommen → ist gekommen, fahren → ist gefahren) or a change of state (werden → ist geworden, einschlafen → ist eingeschlafen, sterben → ist gestorben). Also use sein with sein itself and bleiben. Everything else — transitive verbs, stative verbs, reflexive verbs — uses haben: machen → hat gemacht, sehen → hat gesehen, haben → hat gehabt. Regional note: southern German and Austrian dialects use sein with liegen, sitzen, and stehen; standard High German uses haben for these three.

There are four patterns. (1) Regular weak verbs: ge- + stem + -t → machen → gemacht. (2) Irregular strong verbs: ge- + changed stem + -en → gehen → gegangen, essen → gegessen. (3) Separable verbs: the ge- infix slots between the prefix and the stem → aufstehen → aufgestanden, einkaufen → eingekauft. (4) Inseparable verbs (be-, ge-, ver-, ent-, emp-, er-, miss-, zer-) and -ieren verbs drop the ge- entirely → verstehen → verstanden, besuchen → besucht, studieren → studiert.

Perfekt is the universal spoken past in German — use it for almost everything you say out loud. Präteritum is the written narrative past, dominant in novels, journalism, and formal reports. Three exception verbs prefer Präteritum even in conversation: sein (war, not ist gewesen), haben (hatte), and the modal verbs (konnte, wollte, musste). Northern Germany leans more toward Präteritum in everyday speech than the south.

Structurally, German Perfekt is a present perfect: auxiliary conjugated in present tense + past participle. But functionally it covers what English spreads across simple past ("I ate"), present perfect ("I have eaten"), and even past perfect in informal use. Don't map German Perfekt to English present perfect — map it to all spoken past-time reference. The name describes the form, not the usage.

Partizip II sits clause-final, forming the Satzklammer (sentence bracket) with the auxiliary in V2 position: "Ich habe gestern den Film gesehen." In subordinate clauses both pieces flip to the end together: "…weil ich den Film gesehen habe." The auxiliary, which was in V2 in a main clause, moves to the very last slot in a subordinate clause, with the participle just before it.

No — in Perfekt, a separable verb does not split. Instead, ge- is inserted between the prefix and the stem to form one compound word: aufstehen → aufgestanden, einkaufen → eingekauft. The whole participle is one token at the end of the clause; it never splits the way separable verbs do in the present tense ("Ich stehe auf" in present vs. "Ich bin aufgestanden" in Perfekt).

Verbs ending in -ieren (studieren, telefonieren, reparieren, …) skip ge- because they are borrowed Latinate forms — the resulting "gestudiert" would be awkward. Verbs with inseparable prefixes (be-, ge-, ver-, ent-, emp-, er-, miss-, zer-) also skip ge- because the unstressed prefix already fills that slot: besuchen → besucht, verstehen → verstanden, gefallen → gefallen. The rule: any verb whose first syllable is unstressed does not receive a ge- prefix in the Partizip II.

Technically yes, but written narrative German strongly prefers Präteritum. The standard approach is: Präteritum for the narration ("Er ging ins Zimmer. Das Licht war aus.") and Perfekt for dialogue within the story ("Ich habe heute nichts gegessen," sagte sie.). Keep sein, haben, and modal verbs in Präteritum even inside otherwise Perfekt-heavy narration — "war", "hatte", "konnte" sound natural; "ist gewesen" in narration does not.