Cuando una tarea es difícil, intento no rendirme y busco otra manera de entenderla.

Because cuando without an accent is being used as a conjunction meaning when.

• Cuando una tarea es difícil... = When a task is difficult...

With an accent, cuándo is used in direct or indirect questions:

• ¿Cuándo estudias? = When do you study?
• No sé cuándo viene. = I don’t know when he’s coming.

So here, since it is not a question, cuando is correct.

Yes, Spanish sometimes omits the article, but in this sentence una tarea sounds natural because it means a task / an assignment in a general, countable sense.

• Cuando una tarea es difícil... = When a task is difficult...

Using una makes it sound like any given task. If you removed it, the sentence would feel less natural in standard Spanish here.

Also, tarea can mean:

• task
• assignment
• homework (depending on context)

Both can exist, but they are not exactly the same.

• es difícil = it is difficult in general / by nature
• está difícil = it is difficult right now / in the current situation

In this sentence, es difícil fits better because it describes the task as difficult in a general sense.

Compare:

• La tarea es difícil. = The assignment is difficult.
• La situación está difícil. = The situation is difficult right now.

A learner will often hear both, but es difícil is the safest choice here.

Rendirse is a reflexive verb that usually means to give up or to surrender.

So:

• intento no rendirme = I try not to give up

The verb is rendirse, and in the sentence it appears as rendirme because the reflexive pronoun me is attached to the infinitive rendir.

This is very common in Spanish:

• quiero levantarme = I want to get up
• voy a acostarme = I’m going to go to bed
• intento no rendirme = I try not to give up

In Spanish, when you use an infinitive, object and reflexive pronouns can attach to the end of it.

So:

• rendirme = rendir + me

You cannot say me rendir.

With the structure intentar + infinitive, the normal form is:

• intento rendirme
• intento no rendirme

If the verb were conjugated instead, then the pronoun would go before it:

• no me rindo = I do not give up

So compare:

• Intento no rendirme.
• No me rindo.

Both are correct, but the grammar is different.

Because no is negating the infinitive phrase:

• intento no rendirme = I try not to give up

If you said:

• intento rendirme

that would mean:

• I try to give up

So the no is essential to the meaning.

Busco is the present simple, and in Spanish it is often used where English might also use a more continuous form.

Here, busco expresses a habitual or typical reaction:

• When a task is difficult, I try not to give up and I look for another way to understand it.

Spanish often prefers the simple present for general habits:

• Leo por la noche. = I read at night / I do read at night.
• Cuando algo es difícil, busco una solución. = When something is difficult, I look for a solution.

Estoy buscando would sound more like something happening right now at this very moment.

Otra manera de entenderla means another way of understanding it or another way to understand it.

The structure is:

• manera de + infinitive

This is very common in Spanish:

• una forma de aprender = a way of learning / a way to learn
• una manera de hacerlo = a way of doing it / a way to do it

So:

• otra manera de entenderla = another way to understand it

You may also hear otra forma de entenderla, which means almost the same thing.

La refers back to una tarea.

Since tarea is feminine singular, the direct object pronoun is la:

• la tarea → la

So:

• entenderla = to understand it
• literally: to understand her/it, but here it clearly means it, referring to the task

This kind of pronoun replacement is very common:

• Tengo una tarea. = I have an assignment.
• Quiero entender la tarea. = I want to understand the assignment.
• Quiero entenderla. = I want to understand it.

For the same reason as in rendirme: with an infinitive, pronouns can be attached to the end.

So:

• entenderla = entender + la

You could also sometimes place pronouns before a conjugated verb, but not before the infinitive on its own in this structure.

Correct:

• quiero entenderla
• voy a hacerla
• intento resolverla

Not correct:

• quiero la entender

Because Spanish often drops subject pronouns when the verb ending already shows who the subject is.

• intento = I try
• busco = I look for

Since the -o ending makes it clear that the subject is yo, Spanish normally leaves yo out unless you want emphasis or contrast.

So:

• intento no rendirme y busco... sounds natural.
• yo intento... y yo busco... is grammatically possible, but usually unnecessary.

No. Difícil is an adjective that does not change for masculine/feminine in the singular.

So you get:

• un libro difícil
• una tarea difícil

It only changes for number:

• un libro difícil
• unos libros difíciles
• una tarea difícil
• unas tareas difíciles

Many Spanish adjectives work like this.

Because this sentence describes a general, habitual situation.

• Cuando una tarea es difícil, intento no rendirme...
• When a task is difficult, I try not to give up...

With cuando, Spanish uses:

• indicative for habitual, repeated, or known situations
• subjunctive for future or uncertain events

Compare:

• Cuando una tarea es difícil, busco otra manera de entenderla.
  Habitual/general → indicative

• Cuando una tarea sea difícil, buscaré otra manera de entenderla.
  Future possibility → subjunctive

So in your sentence, es is correct because the speaker is talking about what they generally do.