saikidousitara, waifai no setuzoku mo yoku natta.

したら is the past short form + ら pattern, which often means when, after, or if something happens.

So:

• 再起動する = to restart / reboot
• 再起動した = restarted
• 再起動したら = when I restarted it / after restarting it / if you restart it

In this sentence, the most natural feeling is after restarting it or when I restarted it.

再起動 means restart or reboot.

It is made from:

• 再 = again
• 起動 = startup / booting up

As a noun, 再起動 means a restart.
With する, it becomes a verb:

• 再起動する = to restart something / to reboot

So 再起動したら comes from 再起動する.

ワイファイ is just the Japanese katakana spelling of Wi-Fi.

Katakana is commonly used for:

• foreign loanwords
• brand-like terms
• tech words

So ワイファイ is very normal in everyday Japanese. You may also sometimes see:

• Wi-Fi
• wifi
• 無線LAN in more technical or formal contexts

But ワイファイ is common and natural in casual speech and writing.

接続 means connection.

Here, ワイファイの接続 means:

• the Wi-Fi connection
• literally, Wi-Fi’s connection or connection of Wi-Fi

The particle の links nouns together. In English, we often translate it as:

• of
• 's
• or just by turning it into a noun phrase like Wi-Fi connection

So:

• ワイファイ = Wi-Fi
• 接続 = connection
• ワイファイの接続 = Wi-Fi connection

も means also or too.

So 接続も suggests that the Wi-Fi connection also improved, probably in addition to something else that got better after the restart.

For example, the implied context might be:

• the device got faster, and
• the Wi-Fi connection also improved

Even if that earlier thing is not stated in this sentence, も tells you there is some sense of also.

This is because よく is the adverb form of いい / よい.

• いい / よい = good
• よく = well / better

Since なった comes from なる and means became, you need the adverb form before it:

• よくなる = to get better / to improve

So:

• 接続がよくなった = the connection got better

You cannot say よいなった here.

なった is the past form of なる, which means to become.

So:

• よくなる = to become good / to improve
• よくなった = became better / improved

This shows a change of state. The connection was one way before, and after the restart, it became better.

Yes. Japanese often leaves out things that are understood from context.

In 再起動したら、ワイファイの接続もよくなった。, the sentence does not explicitly say:

• what was restarted
• whose Wi-Fi connection it is
• who did the restarting

From context, it might mean something like:

• After I restarted my phone, the Wi-Fi connection also improved.
• After restarting the router, the Wi-Fi connection also got better.

Japanese often sounds natural this way when the context is clear.

You might expect 接続がよくなった, and that would be perfectly natural.

Here, 接続もよくなった uses も instead of が. In many cases, も replaces が, は, or を depending on the sentence.

So:

• 接続がよくなった = the connection improved
• 接続もよくなった = the connection also improved

The key difference is that も adds the meaning of also.

Grammatically, たら can mean either if or when/after, depending on context.

In this sentence, the most natural interpretation is when/after because it sounds like the speaker is describing a real result that happened:

• After restarting it, the Wi-Fi connection also improved.

If it were advice, it could sound more like if:

• 再起動したらよくなるよ。
• If you restart it, it’ll get better.

So たら is flexible, and context decides the best translation.

No. The spaces here are probably just added for readability for learners.

Normal Japanese would usually be written like this:

再起動したら、ワイファイの接続もよくなった。

Japanese normally does not use spaces between words the way English does.