higaeri de kyouto he kankou ni iku nara, sihatu ni notta hou ga ii desu.

日帰り means a day trip—going somewhere and coming back on the same day.

The particle で shows the condition/manner in which the action happens. So 日帰りで京都へ観光に行く means something like:

• go sightseeing to Kyoto as a day trip
• go to Kyoto for sightseeing and return the same day

Here, で is not the location particle. It is linking 日帰り to the rest of the sentence and showing the trip is being done as a day trip.

Both へ and に can mark a destination, so both are possible in many cases.

• 京都へ行く
• 京都に行く

The difference is small:

• へ emphasizes the direction toward a place
• に emphasizes the destination/arrival point

In this sentence, 京都へ観光に行く sounds very natural. It focuses on going to Kyoto for sightseeing. If you said 京都に観光に行く, that would also be grammatical and natural.

In 観光に行く, the particle に marks the purpose of going.

So:

• 観光に行く = go for sightseeing
• 勉強に行く = go to study
• 買い物に行く = go shopping

A noun plus に行く often means go somewhere in order to do that activity.

So 京都へ観光に行く is literally like go to Kyoto for sightseeing.

なら means if it is the case that..., if you are going to..., or if you’re talking about...

So 京都へ観光に行くなら means:

• if you’re going to Kyoto for sightseeing
• if you plan to go sightseeing in Kyoto

This なら often gives advice based on a condition that is already being considered. It can sound like:

• If that’s what you’re going to do, then...
• In that case...

So the sentence has a natural advice nuance:
If you’re going to Kyoto on a day trip for sightseeing, then it’s better to take the first train.

Both can mean if, but they are not exactly the same.

• 行くなら: if you’re going / if you plan to go / if that’s the idea
• 行ったら: often when you go / if you go and then...

In this sentence, 行くなら is better because the speaker is giving advice about a plan that has not happened yet.

• 日帰りで京都へ観光に行くなら、始発に乗ったほうがいいです。
  = If you’re going to do that, you should take the first train.

If you used 行ったら, it could sound more like talking about what happens after actually going, so it is less natural for this kind of advance advice.

始発 means the first train of the day (or the first bus, subway, etc., depending on context).

In this sentence, it almost certainly means:

• the first train
• the earliest train

So 始発に乗ったほうがいいです means you should take the first train.

The verb 乗る uses に for the vehicle you get on.

Examples:

• 電車に乗る = get on / ride a train
• バスに乗る = get on / ride a bus
• 始発に乗る = get on the first train

This is just how 乗る works in Japanese. English learners often want to use を, but with vehicles, 乗る normally takes に.

Right—it does not mean past here.

The pattern verb past form + ほうがいい is a grammar pattern meaning:

• had better do
• it would be better to do
• should do

So:

• 乗ったほうがいい = it would be better to take
• 早く行ったほうがいい = you should go early
• 休んだほうがいい = you should rest

The past form is part of the grammar pattern and does not make the sentence past in meaning.

No, it is usually advice or a recommendation, not a direct command.

始発に乗ったほうがいいです means something like:

• You’d better take the first train
• It would be better to take the first train
• You should take the first train

It can sound fairly strong depending on context, but it is still softer than a direct order like 始発に乗ってください or 始発に乗るべきです.

So the speaker is advising what is probably the best choice for a day trip.

Japanese often leaves out the subject when it is clear from context.

In this sentence, the implied subject is probably you:

• If you’re going to Kyoto for sightseeing as a day trip, you should take the first train.

But Japanese does not need to say あなたは unless there is a special reason to emphasize it. In normal conversation, leaving it out sounds more natural.

It breaks down like this:

• 日帰りで = as a day trip
• 京都へ = to Kyoto
• 観光に行く = go for sightseeing
• なら = if / if that’s the case
• 始発に乗ったほうがいいです = it’s better to take the first train

So the structure is:

[If you go to Kyoto for sightseeing as a day trip], [it is better to take the first train].

A very literal gloss would be:

As a day trip, to Kyoto, for sightseeing, if going, the first train, riding it would be better.

That sounds unnatural in English, but it shows how the Japanese sentence is built.

Yes, it is natural and clear.

A Japanese speaker would normally write it without spaces:

日帰りで京都へ観光に行くなら、始発に乗ったほうがいいです。

It sounds like practical advice. For example, someone might say this because a day trip to Kyoto gives you limited time, so leaving very early is a good idea.