Quote: »I know that I'll use "sein" verb in the 1. and 4. sentence and "haben" verb for other ones.« - Sorry that's wrong. It's correct for the sentences 1, 2 and 3, but wrong for sentence 4. Here are the correct sentences:
- Von 1982 bis 1990 ist Steffi mit Jens und Kevin in die Thomas Schule gegangen.
- Ihr Abitur hat sie 1990 gemacht.
- Im Studium hat sie ihren Traumman Markus getroffen.
- 1996 haben Markus und Steffi geheiratet.
Quote: »But I didn't understand that what is the verb conjugation. Will I conjugate years, places with "hat" and "ist" always?«
Don't mix up:
Konjugation (in English: conjugation)
This is what you do with verbs to grammatically adjust them to ...
- number of the subject (singular or plural)
- person of the subject (1st, 2nd or 3rd person)
- honorable form (Du or Sie, only for 2nd person)
- tense (German has 6 tenses)
- mode (Indikativ, Konjunktiv (in Engl.: subjunctive), Imperativ)
- voice (active or passive)
Deklination (english: declension)
This is what you do with nouns, and some words that accompany nouns (adjectives, pronouns, numerals, article etc.) to adjust them to ...
- grammatical gender (The gender of nouns is fix, the gender of other words must match with the gender of the noun to which it belongs)
- number (singular or plural)
- grammatical case (nominative, genitive, dative or accusative)
- comparison (positive, comparative, superlative) (only for adjectives and participles)
So, the only category that conjugation and declination have in common is the number (singular/plural). So you never conjugate years or places because they are nouns.
The umbrella term for Kunjugation and Deklination is Flexion or Beugung (in English: inflection)
I think the question you really wanted to ask is this:
When do I have to use a form of haben and when a form of sein when I use verbs in the German tense Perfekt?
The answer is: This depends on the verb only. It does not depend on the subject or other objects. This is an intrinsic property of each verb. You have to learn for each individual verb which auxiliary verb it needs. This is how German native speakers deal with auxiliary verbs, and it is very similar to learning the gender of each individual noun.
But learning the right auxiliary verb is easier than learning the nouns of genders, because you can group the verbs to clusters with similar usage and all verbs within such a cluster use the same auxiliary verb.
But be aware, that there is not much logic behind this system. There are even regional differences:
- In most parts of Germany you say: »Ich habe gesessen«.
- In Austria, Switzerland and southern parts of Germany people say: »Ich bin gesessen«.
(Same for liegen, stehen and other verbs that indicate a person's posture.)