I speak Norwegian. She speak*s* Swedish. We sp*o*ke Danish.
Speak is an irregular verb. It has the -s and -ing endings, but 'speaked' would be wrong. Verbs which involve vowel changes (like spoke and spoken) are sometimes called strong verbs.
The infinitive is the form of the verb one finds in the dictionary, usually ending in -e or a stressed vowel, e.g. å snakke or å tro. If you leave off å it is known as the bare infinitive.
Adjectives describe objects, people or states.
The ball is red. There is a green ball.