La nouvelle clôture est plus solide que l’ancienne, mais le portail grince encore.

In French, adjective position is not always the same.

• Some common adjectives often go before the noun, especially ones about beauty, age, goodness, and size.
  
  • nouvelle clôture = new fence
• Many other adjectives usually go after the noun.
  
  • clôture solide = solid fence

So:

• la nouvelle clôture = the new fence
• plus solide = more solid

This is normal French word order, not something special about this sentence.

French often leaves out a noun when it is already understood from the context.

Here, l’ancienne means the old one, with clôture understood:

• La nouvelle clôture est plus solide que l’ancienne.
• Literally: The new fence is more solid than the old one.

This works in English too:

• the new fence ... than the old one

Because clôture is feminine singular, the adjective becomes feminine singular too:

• ancien → masculine singular
• ancienne → feminine singular

This is the standard French pattern for comparisons:

• plus ... que = more ... than
• moins ... que = less ... than
• aussi ... que = as ... as

So:

• plus solide que l’ancienne = more solid than the old one

Here:

• plus = more
• solide = solid
• que = than

Because French nouns have grammatical gender.

• clôture is feminine → la clôture
• portail is masculine → le portail

That also affects adjectives and pronouns connected to them:

• la nouvelle clôture → feminine adjective nouvelle
• l’ancienne → feminine adjective again, referring back to clôture

So the articles are not chosen by natural gender, but by the noun’s grammatical gender.

They are related, but not the same thing.

• clôture = fence, enclosure, boundary fencing
• portail = gate, usually a larger or more formal gate

So the sentence is talking about two parts of the property:

• the fence is stronger now
• but the gate still squeaks

A smaller gate can also be portillon, but portail is very common for a main gate.

Here, encore means still.

• le portail grince encore = the gate still squeaks

Depending on context, encore can also mean again:

• Fais-le encore. = Do it again.

But in this sentence, still is the natural meaning because it contrasts with the improvement in the fence:

• the fence is better now,
• but the gate still squeaks.

French often places encore after the verb or near the end of the clause.

So:

• Le portail grince encore = The gate still squeaks

That word order is very natural in French. English usually puts still before the main verb:

• The gate still squeaks

French does not have to match English word-for-word.

Grince is the present tense of the verb grincer.

Conjugation:

• je grince
• tu grinces
• il / elle / on grince
• nous grinçons
• vous grincez
• ils / elles grincent

In the sentence:

• le portail grince = the gate squeaks / is squeaking

In ordinary French, the present tense can often match either English simple present or present progressive, depending on context.

Because la becomes l’ before a vowel sound.

• la ancienne would sound awkward
• so French uses l’ancienne

This is called elision.

You see it with both le and la:

• le ami → l’ami
• la ancienne → l’ancienne

Even though ancienne is feminine, the article becomes l’ before the vowel.

In a comparison like this, plus is usually pronounced ploo with the s pronounced:

• plus solide ≈ ploo so-leed

That helps distinguish it from the negative use of plus, where the final s is often silent:

• Je ne veux plus. = I don’t want any more.

So in this sentence, because plus means more, learners usually pronounce the s.

Mais means but and introduces a contrast.

The sentence first gives a positive point:

• La nouvelle clôture est plus solide que l’ancienne
  = The new fence is stronger than the old one

Then it adds a remaining problem:

• mais le portail grince encore
  = but the gate still squeaks

So mais connects two ideas that contrast with each other.

Grammatically, it can exist in some contexts, but it is not the normal everyday way to say the new fence here.

The natural phrase is:

• la nouvelle clôture

With many common adjectives like nouveau / nouvelle, French usually puts the adjective before the noun.

So for ordinary usage, a learner should use:

• un nouveau portail
• une nouvelle clôture

not usually:

• une clôture nouvelle

Some French adjectives have the same form in masculine and feminine.

Solide is one of them:

• masculine singular: solide
• feminine singular: solide

So even though clôture is feminine, the adjective stays solide.

Compare that with ancien / ancienne, where the feminine form is clearly different.

So:

• un mur solide
• une clôture solide

Both use solide.