Learn Hardcore French: Dans la forêt, nous suivons un sentier facile.

Yes. You can also say: Nous suivons un sentier facile dans la forêt. Putting Dans la forêt first just sets the scene/emphasis. The comma after a short fronted phrase is stylistic; many writers include it, but it’s optional here.

Why is it dans (in) and not en or à?

dans la forêt = inside a specific forest, the physical interior.
en forêt = in woodland/forest in general, often for habitual or generic contexts (e.g., hunting, hiking).
à la forêt is not used for “in the forest.” Compare: entrer dans la forêt (enter the forest), se promener en forêt (go walking in the woods, generally), à la montagne / en montagne both exist with nuances, but with forest you use dans la forêt or en forêt.

Why is it la forêt and not une forêt?

La forêt suggests a specific forest known in context (very likely the one the speakers are in). Une forêt would mean “a forest” (unspecified). Without an article, en forêt refers to the environment “in the woods/forest” in a general sense.

What are the genders of forêt and sentier, and what does that change?

forêt is feminine: la forêt, une forêt, cette forêt.
sentier is masculine: le sentier, un sentier, ce sentier. Adjectives must agree: un sentier facile (masc. sg), des sentiers faciles (masc. pl), une forêt dense (fem. sg), des forêts denses (fem. pl).

Why is the adjective facile placed after the noun?

Most French adjectives go after the noun. Facile is normally post-nominal. A few common adjectives (BANGS: beauty, age, number, goodness, size) tend to come before, e.g., petit, grand, beau, vieux, jeune, bon, mauvais, nouveau, joli. So: un beau sentier facile is natural, but un facile sentier sounds literary/odd.

Does facile change with gender or number?

Singular: facile for both masculine and feminine.
Plural: faciles. Examples: un sentier facile, des sentiers faciles, une randonnée facile, des randonnées faciles.

Why is suivons (simple present) used for “are following”?

French simple present covers both English simple and progressive. Nous suivons can mean “we follow” or “we are following.” If you want to insist on the ongoing nature, use Nous sommes en train de suivre un sentier facile, but it’s not required.

How do you conjugate suivre?

Present: je suis, tu suis, il/elle suit, nous suivons, vous suivez, ils/elles suivent
Past participle: suivi (with auxiliary avoir)
Imparfait: je suivais, etc.
Future: je suivrai, etc.
Imperative: Suis ! Suivons ! Suivez !

Isn’t je suis also “I am”? How do you tell “I follow” from “I am”?

Yes, je suis means both “I follow” (from suivre) and “I am” (from être). They are pronounced the same; context decides:

Je suis un sentier. = I follow a path.
Je suis content. = I am happy. Note the imperative difference: être → Sois prudent !; suivre → Suis le sentier !

Any pronunciation tips for this sentence?

dans: nasal vowel [ɑ̃]; final -s silent.
la forêt: [la fɔʁɛ]; the -t is silent; the r is uvular; ê gives an open “eh.”
nous: [nu]; final -s silent.
suivons: [sɥivɔ̃]; ui = [ɥi] (like in huit); -ons = nasal [ɔ̃].
un: nasal [œ̃].
sentier: [sɑ̃tje]; en = nasal [ɑ̃]; tier = [tje]; the written final -r in -ier words isn’t pronounced.
facile: [fasil]. Natural flow (approx.): [dɑ̃ la fɔʁɛ, nu sɥivɔ̃ zœ̃ sɑ̃tje fasil].

Are there liaisons in this sentence?

Yes, you’ll typically make a liaison between suivons and un: suivons un → [sɥivɔ̃‿zœ̃]. No liaison in dans la, and you wouldn’t normally make one in sentier facile.

Could I use marcher instead of suivre?

Different idea:

marcher (sur) le sentier = to walk (on) the path.
suivre un sentier = to follow/keep to a path (to take that route). Your sentence emphasizes following the route, so suivre is the right verb.

Can I replace nous with on?

Yes. On suit un sentier facile. This is very common in everyday speech and means “we.” Be careful: on takes third-person singular verbs (not on suivons).

How do I say this in the past or future?

Past (passé composé): Nous avons suivi un sentier facile.
Past (imperfect, ongoing/habitual): Nous suivions un sentier facile.
Future: Nous suivrons un sentier facile.
Near future: Nous allons suivre un sentier facile. Casual speech with on is also common: On a suivi…, On va suivre…

Are there close synonyms for sentier, and what’s the nuance?

sentier: footpath/trail (often narrow, for walking).
chemin: path/way/road (very general; can be wider).
piste: track/trail (ski run, dirt track, bike lane: piste cyclable).
allée: path/avenue in a park/garden/estate.
Less common: sente (literary/regional, narrow path), itinéraire (itinerary/route, abstract), trace (a track/trace left on the ground).

Why does forêt have a circumflex (ê)? Does it change anything?

The ê often marks a historical lost -s (compare English “forest”). It slightly opens the vowel sound ([ɛ]) but doesn’t change the meaning. Unlike some optional circumflexes on i/u, the one in forêt is retained in modern spelling.

If I add more adjectives, where do they go?

General pattern: BANGS-type adjectives before the noun; descriptive ones after.

un beau sentier facile et ombragé = a beautiful, easy, shady path. Placing facile before the noun is unusual; keep it after.

Anything special about agreement with the past participle suivi?

With avoir, the past participle agrees with a preceding direct object:

Le sentier que nous avons suivi (masc. sg, no -e/-s).
Les sentiers que nous avons suivis (masc. pl, add -s).
But: Nous avons suivi un sentier (no preceding object → no agreement: suivi).