mosi saizu ga awanakattari, iro ga hadesugitari sitara, mise ni mou itido yotte, tenin ni teinei ni soudansimasu.

もし marks the sentence as a hypothetical “if” situation. It often appears with conditional forms such as 〜たら, 〜ば, or 〜なら.

So here:

• もし … したら = if … happens / if that’s the case

It is not always required, but it makes the conditional feel clearer and more natural.

Yes, both contribute to the if meaning, but they do different jobs:

• もし = an optional word that signals a hypothetical situation
• 〜たら = the actual grammatical conditional form

So:

• もし = “suppose / if”
• …したら = “if it happens that …”

Using both together is very common in Japanese and sounds natural.

This is the pattern:

• A たり
• B たり
• したら

The 〜たり form is being used to give examples of possible situations. In this sentence, it means something like:

• if things happen such as the size not fitting or the color being too flashy

So it is not saying both things must happen. It gives representative examples of possible problems.

A natural way to understand it is:

• If, for example, the size doesn’t fit, or the color is too flashy, …

Because the sentence is not making a simple single conditional like if it doesn’t fit. Instead, it is using the 〜たり listing form.

Compare:

• サイズが合わなかったら = if the size doesn’t fit
• サイズが合わなかったり、色が派手すぎたりしたら = if things like the size not fitting or the color being too flashy happen

So 〜たり is being used to list example conditions, and then したら applies to the whole list.

That is how 〜たり is formed.

For verbs and i-adjectives, you usually attach り to the plain past form:

• 行く → 行ったり
• 食べる → 食べたり
• 合わない → 合わなかったり
• 高い → 高かったり

So even though it looks like a past form, here it is just part of the 〜たり grammar pattern. It does not necessarily mean past time.

Break it down like this:

• 派手 = flashy, showy
• 〜すぎる = too much / excessively
• 派手すぎる = to be too flashy
• 派手すぎたり = being too flashy, among other possible examples

So 色が派手すぎたり means:

• the color being too flashy
• or more naturally: if the color is too flashy

In the pattern 〜たり〜たりする, the する acts as the verb that wraps up the whole list.

So:

• 合わなかったり、派手すぎたりする = to have things such as not fitting or being too flashy
• 合わなかったり、派手すぎたりしたら = if things like that happen

The し is just the stem of する.

It can mean one or more examples like those. It does not require both.

So the sense is:

• if the size doesn’t fit
• or if the color is too flashy
• or if something like that is the case

The 〜たり form is intentionally a bit open-ended.

寄って is the te-form of 寄る.

In this sentence, 寄る means:

• to stop by
• to drop in

So:

• 店にもう一度寄って = stop by the store again, and …

The て-form links this action to the next one:

• stop by the store again and consult the clerk politely

Because 寄る usually takes に when it means to stop by / drop in at a place.

• 店に寄る = stop by the store
• 駅に寄る = stop by the station
• コンビニに寄る = stop by the convenience store

So に marks the destination or place you are dropping in on.

もう一度 means:

• once more
• again

So 店にもう一度寄って means:

• stop by the store again

It suggests the speaker has already been there before and plans to return.

Because 相談する often uses に to mark the person you consult.

• 店員に相談する = consult the store clerk
• 先生に相談する = consult the teacher
• 友達に相談する = ask a friend for advice

So に marks the person you are turning to for help or advice.

It is more specific than just talk to. 相談する usually means:

• to consult
• to ask for advice
• to discuss a problem with someone

So here, the speaker is not merely chatting with the clerk. The idea is:

• I’ll politely ask the clerk for help/advice about the issue

丁寧 is a na-adjective, and when you want to use it adverbially to describe how an action is done, you usually change it to 〜に.

• 丁寧な店員 = a polite clerk
• 丁寧に話す = speak politely
• 丁寧に相談します = consult politely

So 丁寧に describes how the speaker will consult the clerk.

Yes, most naturally the subject is I, even though Japanese leaves it unstated.

The sentence ends with 相談します, which sounds like the speaker’s own plan or action:

• (I) will stop by the store again and politely consult the clerk.

Japanese often omits subjects when they are clear from context.

Possibly, but 〜たら is very natural here because it works well for specific situations that might happen.

• …したら = if that happens / if that turns out to be the case

You might see other conditionals in related sentences, but here たら fits nicely because the speaker is talking about what they will do if those problems come up.

Yes, it is polite / formal-neutral because it ends with 相談します.

Other signs that it sounds careful and appropriate:

• 丁寧に = politely
• the overall phrasing is appropriate for explaining what one would do in a shopping situation

A casual version might end more like:

• 相談する
• 相談するつもり
• 相談してみる

But 相談します is polite and standard.

Yes. 合う means to fit / match / suit depending on context.

So:

• サイズが合う = the size fits
• 服が合う = the clothes suit someone
• 予定が合う = schedules match
• 口に合う = suit one’s taste

In this sentence, because it is サイズ, the meaning is clearly the size fits.