Sia che tu vada dalla farmacista, sia che tu passi dal panettiere, portami qualcosa di caldo.

It is a fixed pattern meaning whether ... or ... / whether ... or whether ....

It introduces two possible situations, and the main clause applies in either case. So the idea is:

• whether you go to the pharmacist
• or whether you stop by the baker

...the speaker still wants the same thing afterward.

This structure is very common in Italian, and it normally takes the subjunctive.

Because after sia che Italian normally uses the present subjunctive.

So:

• che tu vada = subjunctive of andare
• che tu passi = subjunctive of passare

A useful detail: passi looks exactly like the normal tu form of the present indicative, but here its function is still subjunctive because the structure sia che requires it.

Vada makes this easier to notice, because it is clearly not the ordinary indicative vai.

Not strictly. Italian often drops subject pronouns because the verb form already shows the person.

So you could also say:

• Sia che vada dalla farmacista, sia che passi dal panettiere...

The tu is included for clarity, rhythm, or a bit of emphasis. It is perfectly natural either way.

Because da combines with the definite article:

• da + la = dalla
• da + il = dal

Here da means something like to the place/business of or to see a person.

So:

• andare dalla farmacista = go to the pharmacist
• passare dal panettiere = stop by the baker

The article changes because:

• la farmacista is feminine
• il panettiere is masculine

Because with professions meaning to a specific professional/shop, Italian normally uses da + article + profession:

• dal medico
• dal dentista
• dal panettiere
• dalla farmacista

Without the article, da farmacista would usually mean as a pharmacist, not to the pharmacist.

For example:

• Lavora da farmacista = He/She works as a pharmacist.

No. Farmacista is a common-gender noun: the singular form stays the same, but the article changes.

• il farmacista = male pharmacist
• la farmacista = female pharmacist

So in your sentence, dalla farmacista tells you the pharmacist is female.

They are similar, but not identical.

• andare da = to go to
• passare da = to stop by / drop in at

So vada dalla farmacista sounds like actually going there as a destination, while passi dal panettiere suggests stopping there on the way or as part of an errand.

In real life, either verb could be used with either place depending on the nuance you want.

Portami is:

• porta = informal singular imperative of portare
• mi = to me

Together: bring me

In affirmative commands, Italian attaches object pronouns to the end of the verb:

• dammi = give me
• portami = bring me
• compramelo = buy it for me

So portami qualcosa di caldo means bring me something warm/hot.

Because after words like qualcosa, Italian normally uses di + adjective.

Very common patterns are:

• qualcosa di buono = something good
• qualcosa di interessante = something interesting
• niente di serio = nothing serious

So qualcosa di caldo is the normal Italian structure.

Because after qualcosa di, the adjective is normally used in the masculine singular by default:

• qualcosa di bello
• qualcosa di strano
• qualcosa di caldo

There is no specific noun stated, so the adjective does not agree with a visible noun. Italian uses the masculine singular as the default form in this pattern.

Yes, in the standard pattern you repeat the whole structure:

• sia che ...
• sia che ...

That repetition is what creates the paired whether ... or ... meaning.

So sia che tu vada..., sia che tu passi... is the expected, natural form.