There's no need to memorize every form a verb can take! Memorizing patterns, some spelling changes, and a very few totally irregular verbs is sufficient.
Check out
this website to see what they say about irregular verbs. First, they touch on the regular verb endings, and then introduce the irregular patterns that may be encountered in the present tense. (Caution: they have accidentally placed
tener in their list of 'o-ue' "stem changers."
Tener is an 'e-ie' stem-changing verb, BUT it also has an irregular first person form in the present tense. You'll find it correctly placed in their "Irregular '
yo' form with a stem change" list.) This page also introduces spelling changes, but the author doesn't draw attention to all of them.
When the present tense irregulars are learned, you'll be happy to learn that there are only three irregular verbs in the imperfect tense! The preterit tense, however, has many irregular forms, almost all of which involve a changed stem.
When it's time to learn the compound verbs, you only have to learn how to conjugate the auxiliary verb
haber into all the tenses, plus the past participle form of the infinitive (along with some irregular participles).
When you're ready to learn the subjunctive mood, you'll discover why it's very important to know the present tense '
yo' forms, because its stem is used to form the present subjunctive mood. Likewise, the past subjunctive mood is formed from the preterit's third person plural form, so it's also very important to know.
Spanish speakers are probably brought to tears when they are introduced to English strong verbs: sing, sang, sung, or speak, spoke, spoken. So, don't despair.