kono nimotu ha omoi desu kara, erebeetaa wo tukaimasu.

この is a demonstrative adjective meaning “this.” It specifies that you’re talking about a particular piece of luggage close to the speaker. In Japanese, you put この directly before the noun it modifies:

• この荷物 = “this luggage”

は marks the topic of the sentence—what you’re talking about. Here, この荷物 is introduced as the topic (“As for this luggage…”).

• Using が would mark 荷物 as the subject in a new or emphasized context (“It is this luggage that…”).
• Using を would incorrectly mark 荷物 as the object of the verb.

In polite speech, i-adjectives still take です to soften or formalize the statement.

• Plain form: 重い (“is heavy”)
• Polite form: 重いです (“is heavy,” polite)

から is a conjunction meaning “because” or “since.” It attaches to the end of a clause to indicate a reason:

• 重いですから = “because it is heavy”

Both から and ので mean “because,” but they differ in nuance and formality:

• から is more direct and common in spoken Japanese.
• ので is slightly softer and often more formal or written.
  Form changes with polite speech:
• 重いですから (polite + から)
• 重いので (plain + ので) or 重いですので (polite + ので, less common)

The verb 使います (“use”) is transitive, so its direct object—the thing being used—is marked with を.

• エレベーターを使います = “(I) use the elevator.”

Japanese follows a Subject–Object–Verb (SOV) word order. Each clause ends with its verb or copula:

1. この荷物は重いですから (reason clause)
2. エレベーターを使います (main clause with the verb at the end)

Yes, you can drop です in casual/plain speech:

• この荷物は重いから、エレベーターを使う。 (plain)
  However, mixing plain から with polite 使います can feel uneven. Stick to one register (plain or polite) in a single sentence for consistency.