These write-ups make the Japanese verb sound
horrendous. Okay, it is, but to start with it's simple. With any language, Latin or Spanish or German or anything, if you mention every single
paradigm and all the
irregular verbs and all the less-used things like the
subjunctive, it's going to look a ghastly mess.
The key is, how much do you need to know at a basic level? What do you have to learn to begin with? In Japanese it's interesting, it's very different from more familiar European languages, but it is not too complicated at first.
There are two tenses, present and past. Present tense ends in -masu and past tense ends in -masita (also romanized -mashita). The verb to be is always irregular in every language, and you just have to deal with that. It doesn't end in -masu. And these endings are pronounced -mas and -mashta, but I don't want to talk about phonetics.
So tabemasu = eat, mimasu = see or watch, ikimasu = go, hanasimasu = speak. This is polite. It's what you say to Japanese people you meet and are not yet having sex with. And tabemasita = ate, mimasita = saw or watched, ikimasita = went, hanasimasita = spoke.
The verb basically comes at the end (terebi-o mimasu = watch television), but some particles that modify what the sentence is doing can follow it: terebi-o mimasu ka = (question) watching television?, terebi-o mimasu ne = (asking confirmation) watching television, yeah?, terebi-o mimasu yo = (emphasizing) really watching television!
There's no change for person or number of the subject. The verb is the same whether it's I or you or they doing it. That's why I wrote "eat" above, not "I eat" or "you eat" etc.
So there's a present and a past. There's also a polite form and a plain form.
The plain form, which has no -masu and ends in -u or -ru, is what you use when talking to your pet cat or a 5-year-old or your lover, etc. That's tabe-ru, mi-ru, ik-u, hanas-u, etc. But they're also the one you use in polite speech when they're not the main verb (at the end) but a relative clause qualifying a noun. We need some examples for this.
hito-o mimasu = (I) see the person
hito-wa hon-o yomimasu = the person is reading the book
What the second sentence is saying about hito (person) is hon-o yomu (reading the book). So just as you can say "tall person", in Japanese you say "reading the book person": hon-o yomu hito. And in a complete sentence,
hon-o yomu hito-o mimasu = (I) see the person who is reading the book
In Japanese, most adjectives are like verbs. The polite form of "big" is ookii-desu, and the plain form is ookii. (The word desu by itself means "is", but it doesn't mean it here - it's just the polite ending on the adjective/verb.) Just as you use the plain, not polite, form of a verb in a relative clause, you also use the plain form of adjectives when you qualify it:
hon-wa ookii-desu = the book is big
ookii hon = big book = which-is-big book
The negative forms are simple to make too (at first). -masu and -masita (-mashita) become -masen and -masendesita (-masendeshita)respectively. Okay, to be honest the negatives get pretty complicated very soon: I have to struggle to remember how to make the negative of ookii and ookii-desu and taberu, and then you have the past tense forms as well.