Minä opiskelen suomea ensi viikolla.

Yes, you usually can leave out minä.

Finnish verbs show the person clearly, so opiskelen already means I study / I am studying. Because of that, the sentence can simply be:

Opiskelen suomea ensi viikolla.

Including minä is still correct, but it often adds a little more emphasis, contrast, or clarity. For example, Minä opiskelen suomea, mutta hän opiskelee ruotsia = I study Finnish, but he/she studies Swedish.

Opiskella is the dictionary form of the verb, meaning to study.

In the sentence, the verb is conjugated for first person singular (I). In the present tense, that gives:

• (minä) opiskelen = I study / I am studying
• (sinä) opiskelet = you study
• hän opiskelee = he/she studies

So opiskelen is just the I-form of opiskella.

It can mean both.

Finnish does not usually make the same clear distinction that English does between:

• I study
• I am studying

So opiskelen can cover either meaning, depending on context.

In this sentence, because of ensi viikolla (next week), the meaning is something like I will study Finnish next week, even though Finnish is using the present tense form.

Because suomea is the partitive form of suomi.

With the verb opiskella, the thing being studied is very often in the partitive, especially when the action is seen as ongoing, incomplete, or not aimed at a finished result. Studying a language is normally treated this way.

So:

• suomi = Finnish
• suomea = Finnish (partitive form)

This is very common:

• Opiskelen suomea. = I study Finnish.
• Puhun suomea. = I speak Finnish.

Yes. Suomea is the object, but specifically it is in the partitive object form.

In Finnish, objects are not always in just one single form. Depending on the verb and the meaning, an object can appear in different cases. Here, the partitive is used because the action is understood as ongoing and not completed as a whole.

So in this sentence:

• Minä = subject
• opiskelen = verb
• suomea = object
• ensi viikolla = time expression

Viikolla is the adessive form of viikko (week).

The ending -lla / -llä often means something like on, at, or during, depending on context. In time expressions, it often translates naturally as on or just forms part of a phrase like next week.

So:

• viikko = week
• viikolla = on/during the week

And:

• ensi viikolla = next week

Even though English says next week without a preposition, Finnish uses this case ending.

Because ensi is a special word: it is generally indeclinable in expressions like this.

In many Finnish adjective + noun combinations, both words change form together. But ensi usually does not. The noun changes, but ensi stays the same:

• ensi viikko = next week
• ensi viikolla = next week
• ensi vuonna = next year
• ensi kuussa = next month

So ensi viikolla is the normal correct form.

Because Finnish usually uses the present tense for future meaning when the time is clear from context.

There is no normal separate future tense in everyday Finnish like English will study. Instead, Finnish often uses the present tense plus a time word:

• Opiskelen huomenna. = I will study tomorrow.
• Opiskelen ensi viikolla. = I will study next week.

The time expression tells you that the action is in the future.

No, Finnish word order is fairly flexible, although this sentence uses a very common neutral order:

Minä opiskelen suomea ensi viikolla.

You could also say:

• Ensi viikolla opiskelen suomea.
• Suomea opiskelen ensi viikolla.

These are grammatical, but they change the focus or emphasis. The original version is a straightforward neutral sentence.

Also, if the subject is obvious, Finnish often drops minä:

• Opiskelen suomea ensi viikolla.

In natural English, the best translation is usually I will study Finnish next week or I’m studying Finnish next week.

A very literal translation might look like I study Finnish next week, but that sounds less natural in English. Finnish present tense often covers meanings that English expresses with future forms.

So the Finnish sentence is normal, even though English usually prefers a future expression.

A few helpful points:

• Finnish pronunciation is usually very regular.
• Each written vowel is pronounced.
• Double letters are pronounced longer.

For these two words:

• suomea: the vowels are all heard separately: suo-me-a
• viikolla: the ii is long, and the ll is also held a bit longer than a single l

A rough guide:

• suomea ≈ SWO-meh-ah
• viikolla ≈ VEE-kol-la, with a long vee

The stress in Finnish is normally on the first syllable:

• SUO-me-a
• VII-kol-la