Because that's the nature of Spanish; its roots from Latin.
The reason for conjugation is simply to make the sentence make sense. In English we automatically have our verbs match our sentence without even thinking about it. In spanish though, you have to change the verb to fit the number of people you are talking about, and to fit the tense.
For instance you wouldn't say "I buy that book last week"
you would say "I BOUGHT that book last week"
Only if you tell us what verbs to translate and conjugate.
Yes, you do. However, in Spanish you can drop the subject whereas French tends to keep them.
You need to conjugate verbs in most languages. Whether you realize it or not, you conjugate verbs in English as well as in French. Use the French verb "avoir" for example. "j'ai" translates to "I have", and "il a" translates to "he has". If you didn't conjugate it and just left it as "j'avoir" then that would translate to "I to have" which is obviously incorrect.
The imperfect is the most regular tense in Spanish. There are only three irregular verbs in this tense: Ir, Ser, and Ver. To conjugate, add the following to the stem of the verb: Ar verbs: Aba, abas, aba, abamos abais, aban. For Ir or Er verbs: ía, ías, ía, íamos, íais, ían.
When we conjugate verbs, we arrange them according to the subject of the sentence. This means that the verb ending changes to match the subject in terms of person, number, and tense.
tense
I suggest that you look at Le Conjugueur website.
Actually, there are to verbs for 'To be.' They are ser and estar. You conjugate them appropriately to form "is." "es" would be singular: Tú eres muy bonita - you are very pretty Ella es...- she is Ellas son- they are
To conjugate verbs in the nosotros form, you typically drop the infinitive ending (-ar, -er, -ir) and add the appropriate ending for the specific verb tense. For example, in present tense, for -ar verbs you add "-amos" and for -er/-ir verbs you add "-emos" or "-imos".
"Our" is not a verb. It has no conjugation. The Spanish equivalent of "our" is "nuestro/a".
It varies according to the nature of the irregularity and there are many of them. You can find a substantial list, both useful and inexpensive, on pp80-161 of the little volume 'Collins Gem: Spanish Grammar and Verb Tables'.
spanish verbs are either 'ir' 'er' or 'ar'