Die Grammatik ist schwer, aber mit deiner Hilfe verstehe ich sie besser.

Because Grammatik is a feminine noun in German. German nouns have grammatical gender, so you have to learn each noun together with its article:

• der = masculine
• die = feminine
• das = neuter

So the correct form is die Grammatik.

Because schwer comes after the verb ist and describes the subject in a predicate phrase.

After verbs like sein, werden, and bleiben, adjectives usually do not take adjective endings.

So:

• Die Grammatik ist schwer. = correct
• Die Grammatik ist schwere. = incorrect

Compare:

• schwere Grammatik = difficult grammar
• Die Grammatik ist schwer = the grammar is difficult

Yes. schwer can mean both heavy and difficult, depending on context.

In this sentence, Die Grammatik ist schwer clearly means the grammar is difficult, not heavy.

German often uses schwer this way, especially with abstract things like:

• Eine schwere Frage = a difficult question
• Deutsch ist schwer = German is difficult

Because aber joins two main clauses here:

• Die Grammatik ist schwer
• mit deiner Hilfe verstehe ich sie besser

In German, when two independent main clauses are connected with aber, a comma is normally used.

So the comma helps separate the two complete thoughts.

Because the preposition mit always takes the dative case.

Hilfe is feminine, and the possessive word dein has to change to match feminine dative singular:

• nominative: deine Hilfe
• dative after mit: mit deiner Hilfe

So:

• mit deiner Hilfe = correct
• mit deine Hilfe = incorrect

Because deiner is already acting as the determiner.

In English, your help also does not need an article like the. German works similarly here:

• deine Hilfe = your help
• not die deine Hilfe

The possessive word deiner already gives the noun the necessary information about gender, number, and case.

Because German main clauses follow the verb-second rule.

In the second clause, the phrase mit deiner Hilfe has been moved to the front for emphasis. Once that happens, the finite verb must still stay in the second position:

• Mit deiner Hilfe = position 1
• verstehe = position 2
• ich = comes after the verb

So:

• ... aber mit deiner Hilfe verstehe ich sie besser. = correct

If the clause started with ich, then you would say:

• ... aber ich verstehe sie mit deiner Hilfe besser.

Both are possible, but the emphasis is slightly different.

Because German pronouns follow the grammatical gender of the noun, not natural gender the way English usually does.

Since Grammatik is feminine, the pronoun referring to it is sie.

So even though English says it, German says sie because die Grammatik is feminine.

Here, sie is in the accusative singular feminine.

It is the direct object of verstehe:

• ich verstehe sie = I understand it

The subject is ich, and the thing being understood is sie, referring back to die Grammatik.

A useful detail: for feminine singular, sie looks the same in nominative and accusative, so you identify its case by its function in the sentence.

Besser is the comparative form of gut, and here it functions like an adverb: better.

In German word order, short pronouns like sie often come before adverbs like besser, so this sounds natural:

• ich verstehe sie besser

Putting besser near the end is very common in this kind of sentence.

So the structure is:

• verstehe = verb
• ich = subject
• sie = object pronoun
• besser = adverb/comparative

It means better in a general sense, even though German does not state the full comparison explicitly.

The idea is:

• better than before
• better than without your help
• better now

German, like English, often leaves that comparison understood from context.

Yes. For example:

• Aber ich verstehe sie mit deiner Hilfe besser.

This is also grammatical. The difference is mainly emphasis:

• Mit deiner Hilfe verstehe ich sie besser emphasizes with your help
• Ich verstehe sie mit deiner Hilfe besser sounds a bit more neutral

German often moves a phrase to the front to highlight it, while still keeping the verb in second position.