Deja el bolso en el sofá y cierra la puerta, por favor.

They’re affirmative informal commands (the tú imperative):

• dejar → deja (leave / put)
• cerrar → cierra (close)
  In Spain, you use these when speaking to one person you address as tú (a friend, family member, child, etc.).

Use usted commands:

• Deje el bolso en el sofá y cierre la puerta, por favor.
  Deje and cierre are the formal imperative forms.

In Spain, plural informal is vosotros:

• Dejad el bolso en el sofá y cerrad la puerta, por favor.
  Plural formal is ustedes:
• Dejen el bolso en el sofá y cierren la puerta, por favor.

en is commonly used for “in/on/at” depending on context, and Spanish often uses en where English would pick a more specific preposition.

• Deja el bolso en el sofá = leave/put the bag on the sofa (normal phrasing).
  If you want to emphasize “on top of,” sobre is possible: Deja el bolso sobre el sofá, but it can sound more deliberate/precise than needed.

In this context, dejar often means “leave/put (something) somewhere”. English tends to prefer “put” if you’re instructing someone to place it, but Spanish very naturally uses dejar for that idea.

cerrar is a stem-changing verb (e → ie) in many present-tense forms and in the tú command:

• cerrar → cierra
  That’s why it isn’t cerra.

Yes, it’s flexible. All of these are fine:

• Deja el bolso en el sofá y cierra la puerta, por favor.
• Por favor, deja el bolso en el sofá y cierra la puerta.
• Deja el bolso en el sofá, por favor, y cierra la puerta.
  Putting it at the end often feels natural and polite.

Spanish usually omits subject pronouns because the verb form already shows who it is. Adding tú is possible but typically only for emphasis/contrast (and it sounds marked):

• Tú deja el bolso… (as in “You, leave it…”)

el refers to a specific, known bag (the one you have / we’re talking about). un bolso would mean “a bag” in a more general, nonspecific sense.

Often (though usage varies):

• bolso = a handbag/purse or a bag with some structure (also used broadly for “bag”)
• bolsa = a bag/sack, often like a shopping bag or plastic bag
  In everyday Spain Spanish, bolso commonly refers to a handbag.

Yes—puerta is feminine, so it takes la. Noun gender is largely lexical (you learn it with the word). A helpful clue: nouns ending in -a are often feminine (with exceptions).

sofá is masculine: el sofá.
The accent marks the stress: so-FÁ. Without the accent, Spanish stress rules would push stress earlier, so the written accent ensures the correct pronunciation.

y (“and”) is perfectly natural. You could also use sequencing words like:

• Luego / después: Deja el bolso en el sofá y luego cierra la puerta.
  But they’re optional; the original is already idiomatic.

It’s a normal polite request because of por favor, but you can soften more with:

• ¿Puedes…?: ¿Puedes dejar el bolso en el sofá y cerrar la puerta, por favor?
• ¿Podrías…? (more polite): ¿Podrías dejar el bolso en el sofá y cerrar la puerta, por favor?
  Or add cuando puedas (“when you can”): …y cierra la puerta cuando puedas.

Negative commands use a different form (present subjunctive):

• No dejes el bolso en el sofá y no cierres la puerta.
  (Or more naturally: No dejes el bolso en el sofá y no cierres la puerta, por favor.)