Esperanto

As for dropping the gxi, that depends. This depends on the sentence. It's often called the "impersonal" use of a verb. You can drop the gxi when it's impersonal -- that is, when it's talking about something that is just happening - like the weather. Note, however, if you use an impersonal verb, the adjective becomes an adverb.

- Atentu la kafon - ği estas varma.
- Ho kia bela tago. Estas tre varme.

So, in English, every complete sentence needs to have a subject, even if logically no subject exists. The classic example of this is "it's raining." There's no actual "it" in the real world that rains. The word "it" is only there as a grammatical placeholder. What we really mean is "rain is falling down from the sky" or "raining is happening."

In Esperanto for this we would say simply "pluvas." That's the whole sentence. There's no "gxi" required. (In fact, you're required NOT to use it.)

One common reason to use this form is when we're describing the weather - pluvas, sunas hodiaux, estas varme nun. You can also use it to describe the time of day - estas mateno - nun malfruas. (All these sentences would require an "it" in English - IT is raining, IT is sunny, IT is warm now, IT is morning, IT is late now.)

Another common way to use this is to start a sentence with "estas" to mean "there is" or "there are". Estas tri tasoj sur la tablo - there are three cups on the table - three cups are on the table.

The only time you say gxi is when there is an actual gxi doing the action of the verb. So, gxi estas granda (It is big), gxi estas mia horlogxo (it's my clock), gxi estas varma (it [the coffee] is warm.) In all these cases gxi would refer to an actual thing which had already been mentioned or which was strongly implied by the context.

BTW, I didn't spell it out, but the case where we use "estas" to mean "there is" or "there are", it's another case where English requires a word as a "grammatical placeholder" (in this case, "there.")

- Estas tri tasoj sur la tablo = three tasoj estas sur la tablo
- There are three cups on the table = three cups are on the table.

"It is easy to eat chocolate."

"Eating chocolate" (or "manĝi ĉokoladon") is not a noun. It's a verb phrase. In Esperanto, if you want to modify a word that is not a noun or pronoun, you can't use an adjective. You use an adverb.

"Ne estas kulero."

"It is not a spoon" - "Gxi ne estas kulero"
"There is no spoon" - "Ne estas kulero"

In the English constructions "There is <object>" and "There is no <object>" the word "there" is not being used in the same way as it is used when we say "There is my car" as we point to the car. It is a feature of the English language that the expression "God exists" can be rendered as "There is a God" and the latter expression does not mean that we are pointing at Him or otherwise indicating His location.

Prepositions

Keys to Esperanto Prepositions | Esperanto Language Blog
Je - The Esperanto Wildcard | Esperanto Language Blog

al (to)
anstataŭ (instead of)
da (for quantities)
de (of – attachment or belonging)
dum (while)
el (out of, made out of)
ĝis (until),
je (see below)
krom (except, besides)
kun (with)
malgraŭ (in spite of)
per (with, by means of)
por (for)
pri (about)
pro (because)
sen (without)
antaŭ (before, in front of)
ĉe (at, at the home of)
ekster (outside of)
inter (between)
kontraŭ (against)
malantaŭ (behind)
sub (under)
super (over)
sur (on)

Prefixes

10 Prefixes
Opposite	mal-