Verified answer

Can I explain the grammatical structure?

This is a complex sentence, with one independent and one dependent (or subordinate) clause.

The independent clause is "We can provide you with a guideline". I imagine that you understand that clause perfectly.

The dependent clause is "should you request it from us directly". The verb in this clause is "should request". That verb has present tense, simple aspect, and subjunctive mode. It is the subjunctive mode that has you confused.

Subjunctive mode in English is tricky. In this clause, subjunctive mode is only marked by the word order. Normal word order would suggest the indicative mode, as in "you should request it". Some auxiliaries, like "should", suggest the subjunctive mode when placed in the beginning of a clause in the manner of a question, such as "should you request it." This is the same word order as in the question "Should you request it?" This word order makes it clear that the mode is not simply indicative.

Another way to suggest the subjunctive mode is to use a conditional conjunction, such as "if". For instance, "if you should request it." In fact, with a conjunction like "if", the auxiliary "should" is optional, and the clause could read "if you request it".

As you can see, the auxiliary verb "should" is not synonymous with the conditional conjunction "if". They're not even the same part of speech. However, they both do suggest the subjunctive mode. The auxiliary suggests it as a matter of grammar; the conjunction suggests it as a matter of semantics.

Whatever the form, subjunctive mode expresses something that is contrary to fact. In this example, it expresses something that hasn't happened yet and may never happen. You haven't made the request yet. You might not ever make the request. In the event that you do make such a request, we can provide you with a guideline.

"should" in this context is a word that is synonymous (has the same meaning) with "if"

so they are saying that they can provide you with a guideline IF you request it from them.

The sentence itself consists of two clauses:

"We can provide you with a guideline"

and:

"should you request it from us directly"

the second clause is dependant on the first, so you could separate it with a comma for clarity:

"We can provide you with a guideline, if you request it from us directly"

By the way your grammar and sentence structure is exemplary for someone studying English and it makes me feel a little bad for taking my own expression of it for granted hehe, excuse my lack of capitalisation

The "should" could be replaced with "if."

We can provide you with a guideline if you request it from us directly.

Simplified even further:

We can give you a guideline if you ask us directly.

Sometimes you can exchange "should" for "if."