Я попросила подругу помочь мне разобраться, какие шурупы подойдут лучше.

I asked my (female) friend to help me figure out which screws would fit better.

Breakdown of Я попросила подругу помочь мне разобраться, какие шурупы подойдут лучше.

• я: I
• помочь: to help
• мне: me
• лучше: better
• подруга: the female friend
• попросить: to ask
• какой: which
• шуруп: the screw
• разобраться: to figure out
• подойти: to fit

Questions & Answers about Я попросила подругу помочь мне разобраться, какие шурупы подойдут лучше.

Why is it попросила and not попросил?

Because попросила is past tense, feminine singular. It tells you the speaker (or the subject я) is female.
If the speaker were male: Я попросил подругу…
Plural: Мы попросили…

Why is подругу in the accusative case?

With попросить (to ask/request), the person you ask is typically the direct object → accusative: попросить кого? → подругу.
So: Я попросила (кого?) подругу…

Could I say попросила у подруги instead?

Yes, but it changes the structure and nuance:

• попросила подругу помочь… = asked the friend to do something (the friend is the doer).
• попросила у подруги (что?) помощь / совета… = asked from the friend for help/advice (you’re requesting a thing).
  You can also combine: попросила у подруги помочь мне… is possible, but it sounds a bit heavier; the simpler version is more common.

Why is it помочь (perfective) and not помогать (imperfective)?

Помочь is perfective and focuses on achieving a result: help me successfully figure it out.
Помогать would emphasize the process or repeated/ongoing help. In a one-time request like this, помочь is the default.

Why is it помочь мне (dative мне)?

Because помочь governs the dative: помочь кому? → мне.
So мне is not a direct object; it’s the person receiving help.

What does разобраться mean grammatically, and why is it reflexive?

Разобраться is a reflexive verb (ends in -ся) meaning something like to figure things out / to sort it out / to understand the situation.
It’s often used when you “get clarity” yourself: разобраться в чём-то, разобраться, как…, разобраться, какие….

Why is there a comma before какие?

Because какие шурупы подойдут лучше is a subordinate clause (an embedded question) that depends on разобраться:
разобраться, какие… = to figure out which…
Russian uses a comma to separate that clause.

Why is it какие шурупы (nominative) and not some other case?

Inside the embedded clause, шурупы is the subject of подойдут:

• шурупы = the screws
• подойдут = will fit / will be suitable
  So it’s nominative: (какие) шурупы подойдут.

Why is it подойдут (perfective) rather than подходят (imperfective)?

Подойдут is perfective and typically points to a concrete outcome: which screws will be the best choice / will turn out to fit best (for this task).
Подходят is imperfective and more like a general statement: which screws are suitable in general. In “deciding/choosing” contexts, perfective подойдут is very common.

What exactly does подойдут mean here—“fit” or “be suitable”?

Both are possible in English, depending on context. In Russian, подойти covers:

• physical fit: these screws fit
• suitability: these screws will work / are appropriate
  With шурупы, it usually implies suitability/fit for the job.

Why is it лучше and not лучшие?

Лучше is an adverb (comparative) modifying the verb подойдут: will suit (how?) better.
Лучшие would be an adjective modifying шурупы: the best screws. You can say that, but it shifts the wording:

• какие шурупы подойдут лучше = which screws will work better (for my purpose)
• какие шурупы лучше = which screws are better

Is the word order flexible here?

Yes. This sentence is already natural, but you can also hear:

• Я попросила подругу помочь мне разобраться, какие шурупы лучше подойдут.
  Moving лучше earlier adds a bit of emphasis to better. The meaning stays basically the same.

Can I drop мне since я is already the subject?

Not if you want the same structure. Мне is required by помочь (help whom?) and makes it explicit who receives the help.
Without it, помочь разобраться… sounds like help (someone) figure it out, but the “someone” is left implicit and can feel incomplete in many contexts.