לפחות עכשיו אני יודעת איזה אוטובוס מגיע לשם.

Because the speaker is feminine.

• אני יודע = I know (said by a male speaker)
• אני יודעת = I know (said by a female speaker)

Hebrew verbs in the present tense agree with the gender and number of the subject, even with אני.

לפחות means at least.

In this sentence, it gives the idea of if nothing else, at least now... It often adds a slight emotional tone, like relief, resignation, or a small positive point after some uncertainty.

So the feeling is something like:
At least now I know...

Hebrew word order is flexible, and לפחות עכשיו is a very natural combination.

• לפחות עכשיו = at least now
• It emphasizes that now, finally, the speaker knows the information.

You could also hear other word orders in different contexts, but לפחות עכשיו sounds very natural and idiomatic.

Here איזה means which.

So:

• איזה אוטובוס = which bus

In everyday Hebrew, איזה is very common and can sometimes also feel close to what kind of or what depending on context, but here it clearly means which.

Because אוטובוס is masculine singular, and איזה is the common form used before a masculine singular noun.

Common patterns are:

• איזה
  • masculine singular noun
• איזו
  • feminine singular noun
• אילו
  • plural noun

Examples:

• איזה ספר = which book
• איזו עיר = which city
• אילו אוטובוסים = which buses

Because in Hebrew, after verbs like know, you can often directly follow with an indirect question.

So:

• אני יודעת איזה אוטובוס מגיע לשם = I know which bus goes there / arrives there

This is normal Hebrew structure. It works like an embedded question: which bus goes there?

You do not need ש־ here.

Because it agrees with אוטובוס, which is masculine singular.

• אוטובוס = a masculine singular noun
• therefore: מגיע = masculine singular present tense

So:

• איזה אוטובוס מגיע לשם = which bus goes/gets there

If the noun were feminine, the verb would change:

• איזו רכבת מגיעה לשם = which train gets there

It most literally means arrives or gets to, but in natural English this sentence may be translated in several ways depending on context:

• which bus gets there
• which bus goes there
• which bus arrives there

In transportation contexts, מגיע ל... often means reaches / gets to / goes to a place.

So the exact English wording can vary, even though the Hebrew is perfectly natural.

לשם means to there or more naturally there in the sense of to that place.

• שם = there
• לשם = to there / to that place

Examples:

• אני שם = I am there
• אני הולך לשם = I am going there

In your sentence, מגיע לשם means gets there / goes there.

Yes, very normal.

The sentence is built like this:

• לפחות עכשיו = at least now
• אני יודעת = I know
• איזה אוטובוס = which bus
• מגיע לשם = gets there / goes there

So the structure is:

At least now + I know + which bus + gets there

That is a completely natural Hebrew sentence.

Yes, but the verb would change:

• feminine speaker: לפחות עכשיו אני יודעת איזה אוטובוס מגיע לשם
• masculine speaker: לפחות עכשיו אני יודע איזה אוטובוס מגיע לשם

Everything else stays the same.

No, it is not definite by itself, because איזה אוטובוס already means which bus.

When English uses which, Hebrew normally does not add ה־ to the noun:

• איזה אוטובוס = which bus
• not usually איזה האוטובוס

So the noun is understood through the question word איזה, and no definite article is needed.