Me gusta tu compañía cuando estudio español por la tarde.

Because gustar works differently from to like in English.

In Spanish, gustar literally works more like to be pleasing to. So:

• Me gusta tu compañía = Your company/companionship is pleasing to me
• me = to me
• gusta = is pleasing

So the thing being liked, tu compañía, is the grammatical subject, not I.

Because tu compañía is singular.

With gustar, the verb agrees with the thing that is pleasing, not with the person who likes it:

• Me gusta tu compañía → one thing, so gusta
• Me gustan tus ideas → more than one thing, so gustan

Even though me means to me, it does not control the verb form.

They are two different words:

• tu = your
• tú = you

So here tu compañía means your company/companionship.

The accent matters:

• Tu libro = your book
• Tú estudias = you study

Here, compañía means company in the sense of presence, companionship, or being with someone.

In Spanish, compañía can mean:

• companionship / company = the meaning in this sentence
• company / business = in other contexts

So in this sentence it means something like enjoying someone's presence while studying, not a corporation.

Because after verbs like estudiar, the name of a language usually appears without an article.

So Spanish normally says:

• Estudio español
• Aprendo francés
• Habla inglés

Using el would usually sound unnatural here unless there is a special context.

Because after cuando, Spanish often uses a normal conjugated verb to talk about something that happens regularly or generally.

• cuando estudio español = when I study Spanish
• estudio is the yo form of estudiar

Spanish does not always use the progressive form as much as English does.
So English might say when I’m studying Spanish, but Spanish very naturally says cuando estudio español.

You could say cuando estoy estudiando español, but that usually sounds more like a specific ongoing moment.

Por la tarde means in the afternoon or sometimes later in the day / in the evening, depending on context.

In Spain, the day is often divided like this:

• por la mañana = in the morning
• por la tarde = in the afternoon / early evening
• por la noche = at night / in the evening at night-time

So por la tarde is the normal expression for that part of the day. Spanish uses por, not en, in this common time expression.

Yes, Tu compañía me gusta is grammatically possible, but Me gusta tu compañía is more natural as a neutral sentence.

Spanish often places the indirect object pronoun first with gustar:

• Me gusta...
• Te gusta...
• Le gusta...

Putting tu compañía first gives it more emphasis or contrast:

• Tu compañía me gusta, pero el ruido no

So the original order is the most normal one.

The accent mark shows the stress pattern.

Compañía is pronounced with the stress on -ñí-:

• com-pa-ÑÍ-a

Without the accent, Spanish pronunciation rules would suggest a different stress pattern. The written accent tells you exactly where the emphasis goes.

It also helps show that í-a is pronounced in separate syllables.

By itself, it most naturally suggests a habitual or general situation:

• when I study Spanish in the afternoon

It sounds like something that happens regularly, not just once.

If you wanted a very specific one-time event, Spanish would usually add more context:

• cuando estudié español ayer por la tarde
• cuando estaba estudiando español esta tarde

So the present tense here normally gives a general, habitual meaning.

Yes, but it changes the nuance.

• Me gusta tu compañía... focuses on the person's company/presence
• Me gusta estar contigo... focuses more directly on being with you

Both are natural, but the original sentence sounds a little more elegant or affectionate because tu compañía highlights the companionship itself.