1. Let's build a simple sentence composed by a noun or pronoun and a verb:
Ich gehe. (I am going.) – the verb "gehen" was conjugated for 1st person sngular because it is preceded by the pronoun "ich" (I)
Das auto fährt. (The car drives.) – the verb "fahren" (to drive) was conjugated a 3rd person singular because the noun "das Auto" (the car) can be replaced by the pronoun "es" (it).
In a simple sentence the verb stands always on the second place, following a noun or pronoun.
▶ Ex.: Ich gehe in die Schule. (I am going to school.)
In this sentence the verb "gehen" was conjugated for 1st person singular because the action is produced by the pronoun "ich".
If we replace the pronoun with a noun we will always conjugate the verb for 3rd person singular or plural.
▶ Ex.: Der Schüler geht in die Schule. (The student goes to school.)
"der Schüler" (the student) can be replaced by the pronoun "er" (he), this way the verb "gehen" has to be conjugated for 3rd person singular
The same way for all nouns that produce an action:
▶ Ex.: Das Auto fährt langsam. (The car drives slow.)
▶ Der Zug hat verspätung. (The train has late.)
▶ Die Vögel fliegen hoch. (The birds fly high.) – in this example the noun "the birds" can be replaced by the pronoun "they", this way the verb "fliegen" (to fly) has to be conjugated for 3rd person plural.
In an interrogative sentence the verb stands on the first place followed by a noun or pronoun.
▶ Ex.: Kommst du mit uns? (Are you coming with us?)
In this example the verb "kommen" was conjugated for 2nd person singular, because we are adressing a question to another person.
▶ Hat der Zug verspätung? (Has the train late?)
In this example "the train" can bereplaced by the pronoun "it", this means that the verb "haben" will be conjugated for 3rd person singular.
▶ Ist es Kalt draußen? (Is it cold outside?)
Again the verb "sein" is conjugated for 3rd person singular.
2. Let's build a simple sentence composed by a noun, a verb and an adjective:
noun + adjective + verb
▶ Die schöne Frau geht. (The beautiful woman walks.)
▶ Der schöne Mann geht. (The beatiful man walks.)
noun + verb + adjective
▶ Die Frau ist schön. (The woman is beautiful.)
▶ Der Mann ist schön. (The man is beautiful.)
adjective + noun + verb
▶ Eine schöne Frau geht. (A beautiful woman walks.)
▶ Ein schöner Mann geht. (A beautiful man walks.)
Observe how the adjective changes it's endings depending on the position it occupies in the sentence (between the noun and the verb, after the verb, before the noun).
For more explanations, please see the lesson The adjective.
3. Let's build a sentence composed by a definite article, a noun, and an adjective:
definite article + adjective + noun + verb
▶ Die Katze der alten Frau ist verschwunden. (The cat of an old woman disapeared.)
▶ Die Puppe des kleines Kindes ist kaputtgegangen. (The little child's toy got broken.)
verb + definite article + noun
▶ Wir fahren mit dem Zug. (We travel by train.)
▶ Wir treffen uns vor der Kirche! (We meet in front of the church.)
*Please observe the declension of the definite article (der, die, das). Examples: der → dem, die → der, das → dem.
4. Let's build a sentence composed by an indefinite article, a noun, a verb and an adjective:
verb + indefinite article + adjective + noun
▶ Das ist ein schönes Auto. (This is a nice car.)
verb + indefinite article + noun
▶ Ich habe einem Mann meine alte Bücher gegeben. (I gave my old book to an old man.)
▶ Das Buch gehört einem alten Mann. (The book belongs to an old man.)
indefinite article + adjective + noun + verb
▶ Eine junge Frau hat mich angesprochen. (I young woman talked to me.)
Please observe the relation betweem the indefinite article, the adjective and the noun. Also observe how the indefinite article changes it's form according to the gender and case of the noun it precedes: ein, eine, einem etc.