watasi ha sensei ni ikutuka situmon wo simasita.

は marks 私 as the topic of the sentence: as for me....
So 私は sets up what the sentence is about.

Using が would put more focus on I as the subject, as if contrasting with someone else or emphasizing who did the action.

In this sentence, 私は is the most natural neutral choice.

Here, に marks the target/recipient of the action.

So 先生に質問しました means asked the teacher questions or more literally did questions to the teacher.

With verbs involving communication or giving, に often marks the person receiving the action:

• 先生に聞きました = I asked the teacher
• 友だちに話しました = I spoke to my friend

を marks the direct object of する.

質問 is a noun meaning question or questioning, and with する it becomes a verb phrase:

• 質問をする = to ask a question / to ask questions

So:

• 質問 = question(s)
• 質問をしました = asked question(s)

This is a very common pattern in Japanese: noun + をする.

Yes. 質問しました is also natural and very common.

Both are acceptable:

• 先生に質問しました
• 先生に質問をしました

The version with を makes the noun 質問 stand out a little more as the thing being done, but in many everyday situations the difference is very small.

いくつか means some, several, or a few.

It shows that the number is not exact.
So いくつか質問 means several questions.

It is less specific than saying an exact number like:

• 三つ質問 = three questions

Both are possible:

• いくつか質問
• いくつかの質問

Both mean several questions.

The version with の sounds a little more explicitly noun-like, while the version without の is also very natural and common. In everyday Japanese, both are used.

Japanese normally puts the main verb at the end.

A basic Japanese sentence often follows a pattern like:

• topic + other information + verb

So:

• 私は = as for me
• 先生に = to the teacher
• いくつか質問を = several questions
• しました = did / asked

This end-of-sentence verb position is one of the biggest differences from English.

Yes, very often.

If it is already clear from context who is speaking, Japanese usually leaves out 私. So a very natural sentence would be:

• 先生にいくつか質問をしました。

Japanese often omits information that English normally says explicitly.

しました is the polite past form of する.
した is the plain past form.

So:

• しました = polite
• した = casual/plain

You would usually use しました in class, with teachers, with people you do not know well, or in formal writing.

Japanese nouns usually do not change form for singular or plural.

So 質問 can mean:

• a question
• questions

The quantity is understood from context or from words like いくつか. Since いくつか already means several, there is no need for a separate plural ending.

Japanese does not use articles like a and the the way English does.

So 先生 could mean:

• the teacher
• a teacher
• my teacher

The exact meaning depends on context.

Also, Japanese often omits possessives when they are obvious. So if you are talking about your own class, 先生 may naturally be understood as my teacher or the teacher.

No. Standard Japanese is usually written without spaces:

私は先生にいくつか質問をしました。

The spaces here are just for learners, to make the parts of the sentence easier to see.