Basta che tu dica la verità, e io ti aiuto.

Basta che means as long as, provided that, or more literally it’s enough that.

So Basta che tu dica la verità means something like:

• As long as you tell the truth
• You just have to tell the truth
• It’s enough that you tell the truth

It introduces a condition: if that condition is met, the speaker will help.

Because basta che is followed by the subjunctive in Italian.

• tu dici = indicative
• che tu dica = present subjunctive

After expressions like basta che, purché, a patto che, Italian normally uses the subjunctive because the clause expresses a condition or requirement, not a simple factual statement.

So:

• Basta che tu dica la verità = correct
• Basta che tu dici la verità = not standard Italian

Yes, Italian often leaves subject pronouns out, because the verb ending already shows the subject.

So these are both possible:

• Basta che dica la verità
• Basta che tu dica la verità

Adding tu gives a little more emphasis or clarity. It can sound like:

• as long as you tell the truth

In many contexts, Italian speakers would omit it unless they want contrast, emphasis, or extra clarity.

Italian often uses the definite article where English does not.

So:

• dire la verità = to tell the truth

This is the normal expression. Just as English says the truth, Italian says la verità.

You will see this pattern often in fixed expressions:

• avere fame = to be hungry
• avere ragione = to be right
• dire la verità = to tell the truth

Ti means you, as a direct or indirect object pronoun, depending on the verb.

Here it means:

• io ti aiuto = I help you

So:

• io = I
• ti = you
• aiuto = help / I help

Italian object pronouns usually come before the conjugated verb:

• Ti aiuto
• Lo vedo
• Mi chiama

Like tu, io is often optional in Italian.

So you could also say:

• ...e ti aiuto

Adding io gives emphasis. It can suggest something like:

• and I will help you
• and I, for my part, will help you

It makes the speaker’s role a little more explicit.

Italian often uses the present tense to talk about the near future or a future result, especially when the meaning is clear from context.

So:

• e io ti aiuto literally = and I help you
• but naturally it means = and I’ll help you

This is very common in Italian.

You could also say:

• e io ti aiuterò

That would be more explicitly future: and I will help you.

Both are possible, but the present tense often sounds very natural and immediate.

Grammatically, e means and, but in this sentence it connects a condition with its result, so in English it may feel closer to:

• and then
• and in that case
• and I’ll help you

So the meaning is not just simple addition. It is more like:

• Tell the truth, and I’ll help you
• As long as you tell the truth, I’ll help you

The logic of the sentence gives e a slightly conditional-result feel.

Yes. In fact, many Italian speakers would write it without the comma:

• Basta che tu dica la verità e io ti aiuto.

The comma before e is not always necessary in Italian. Here it can mark a pause or make the two parts feel more distinct, but it is not essential.

So both are understandable, though without the comma is often more neutral.

Yes, but it means something slightly different.

• Basta che tu dica la verità = You just need to tell the truth / As long as you tell the truth
• Basta dire la verità = It’s enough to tell the truth / One only needs to tell the truth

The version with che tu dica addresses a specific person more directly.
The infinitive version is more general and less personal.

In your sentence, the version with tu dica fits well because the speaker is speaking directly to someone and then says io ti aiuto.

It is informal, because it uses tu and ti.

If you wanted the formal version, you would normally use Lei and La:

• Basta che Lei dica la verità e io La aiuto.

That means As long as you tell the truth, I’ll help you, but addressed formally.

Notes:

• Lei = formal you as subject
• La = formal you as object pronoun

In modern writing, capitalization of Lei/La is common but not absolutely required in every style.

The verb is dire = to say / to tell.

The present subjunctive is:

• che io dica
• che tu dica
• che lui/lei dica
• che noi diciamo
• che voi diciate
• che loro dicano

So in your sentence:

• che tu dica

This is an important verb to memorize, because it is irregular.

Yes. Dire can mean both say and tell, depending on context.

In dire la verità, the most natural English translation is tell the truth, not say the truth.

So even though the verb is dire, the idiomatic English meaning is:

• tell the truth

This is a good example of why word-for-word translation is not always the best approach.

Yes, a few similar options are possible:

• Purché tu dica la verità, ti aiuto.
• Se dici la verità, ti aiuto.
• A patto che tu dica la verità, ti aiuto.

These are similar, but not identical in tone:

• Basta che = as long as / it’s enough that
• Purché = provided that / as long as
• Se = if
• A patto che = on the condition that

Your original sentence sounds natural and conversational, with a clear sense of that one condition is enough.