Mi facultad está en un campus muy grande, así que a veces tardo bastante en llegar a clase.

Not exactly. In Spain, facultad usually refers to a university school/faculty such as la Facultad de Medicina or la Facultad de Derecho, and sometimes by extension the building or the part of the university where you study.

For an English speaker, it can be a false friend, because English faculty often means the teaching staff. In this sentence, mi facultad means something more like my university faculty/school rather than my professors.

Because this is about location.

In Spanish, estar is normally used to say where something is located:

• Mi facultad está en un campus muy grande. = My faculty is on a very large campus.

By contrast, ser would be used more for identity or defining characteristics:

• Mi facultad es privada.
• Mi facultad es moderna.

So here, está is used because the sentence is saying where it is.

Because un campus muy grande introduces it as a very large campus, not necessarily one already identified for the listener.

• en un campus muy grande = on a very large campus
• en el campus = on the campus

If both speaker and listener already knew exactly which campus was being talked about, en el campus could be natural. But in this sentence, un simply presents it as one campus that happens to be very large.

Yes, campus is commonly used in Spanish, especially in university contexts.

It is usually treated as masculine:

• un campus
• el campus

The plural is commonly:

• los campus

So the form often stays the same in singular and plural.

Así que means so, therefore, or that’s why.

It introduces a result or consequence:

• Mi facultad está en un campus muy grande, así que...
• My faculty is on a very large campus, so...

The idea is:

large campus → it takes time to get to class

It is a very common connector in everyday Spanish.

Because Spanish often drops the subject pronoun when the verb ending already makes the subject clear.

• tardo = I take / I am taking
• yo tardo = I take

The -o ending already tells you it is yo, so yo is unnecessary unless the speaker wants emphasis or contrast:

• Yo tardo bastante, pero ella no.

In the original sentence, leaving out yo sounds completely natural.

This uses the pattern:

tardar + amount/degree + en + infinitive

It means to take time to do something.

So:

• tardo en llegar = I take time to arrive / get there
• tardo bastante en llegar = I take quite a while to get there

You can also use a specific time:

• Tardo diez minutos en llegar a clase. = It takes me ten minutes to get to class.

Here, instead of giving an exact number of minutes, the speaker uses bastante to mean quite a lot / quite a while.

Here it means quite a lot or quite a while.

In this sentence, bastante modifies the verb tardo, so the sense is:

• I take quite a while to get to class

Depending on context, bastante can mean different things:

• Tengo bastante dinero. = I have enough / quite a lot of money.
• Es bastante grande. = It’s quite big.
• Tardo bastante. = I take quite a long time.

So here, bastante is best understood as quite a bit.

Because a clase is a very common expression meaning to class or to class in general.

Spanish often omits the article in set expressions like:

• ir a clase = to go to class
• estar en clase = to be in class
• llegar a clase = to get to class

If you say a la clase, it sounds more specific, as if you mean a particular class session or a specific classroom. The article-free version is the more natural general expression here.

It can move, but the position in the sentence is very natural.

• ...así que a veces tardo bastante en llegar a clase.
• ...así que tardo bastante en llegar a clase a veces.

Both are possible, but putting a veces before the verb is smoother and more common in a sentence like this. It lets the listener know early on that this only happens sometimes, not always.

So the original word order is very natural and idiomatic.