Не злись на меня из-за этой ошибки.

Yes. Злись is a verb form. Its dictionary form is злиться.

In this sentence, злись is the imperative singular form, so it is used when speaking to one person informally and telling them not to be angry or not to get angry.

So:

• злиться = to be angry / to get angry
• злись = be angry / get angry
• не злись = don’t be angry / don’t get angry

The ending -сь is the reflexive ending. With this verb, it is just part of the normal form of the verb and does not need to be translated literally as yourself.

Because не + imperative is the normal way to make a negative command in Russian.

So:

• Злись = be angry
• Не злись = don’t be angry

This is very common in Russian:

• Смотри → Не смотри
• Спорь → Не спорь
• Беспокойся → Не беспокойся

In this sentence, the speaker is telling someone not to be angry with them.

The -сь is the short form of the reflexive ending -ся.

Russian reflexive verbs often end in -ся or -сь:

• злиться
• учиться
• бояться

In some forms, especially after vowels, you often see -сь instead of -ся. Here, злись is simply the correct imperative form of злиться.

It does not mean that the person is literally doing the action to themselves in an obvious English way. With emotion verbs, the reflexive ending is often just part of how the verb works.

Because злиться normally goes with на + accusative when you say who someone is angry with.

The pattern is:

• злиться на кого? на что?

So:

• злиться на меня = to be angry with me
• злиться на друга = to be angry with a friend
• злиться на ситуацию = to be angry about the situation

This is just the standard construction Russian uses with this verb. English speakers often expect something like be angry at or be angry with, and Russian expresses that with на.

Because the preposition на with злиться requires the accusative case, not the dative.

The pronoun я changes like this:

• nominative: я
• accusative/genitive: меня
• dative: мне

Since the pattern is злиться на кого?, we need the accusative form:

• на меня

So на мне would be wrong here.

Here из-за means because of, due to, or over.

So из-за этой ошибки means:

• because of this mistake
• over this mistake

In this sentence, it explains the reason for the anger:

• Не злись на меня из-за этой ошибки
  = Don’t be angry with me because of this mistake.

A useful thing to remember: из-за is a preposition that normally takes the genitive case.

Both words are in the genitive singular because из-за requires the genitive.

Breakdown:

• эта ошибка = this mistake
• after из-за → из-за этой ошибки

Why these forms?

• эта → этой
• ошибка → ошибки

This is feminine singular agreement:

• nominative: эта ошибка
• genitive: этой ошибки

So the adjective/determiner and the noun both change together.

Because эта is the nominative form, but after из-за you need the genitive.

So:

• nominative: эта ошибка
• genitive: этой ошибки

Since ошибка is feminine singular, этой is the correct genitive form of этот here.

This is a very common pattern in Russian: words that modify a noun must match its gender, number, and case.

Yes. Не злись is singular informal, used when speaking to one person you address as ты.

If you want the formal or plural version, use:

• Не злитесь на меня из-за этой ошибки.

So:

• не злись = don’t be angry (to one person, informal)
• не злитесь = don’t be angry (to one person formally, or to several people)

This is a very important distinction in Russian.

Yes, не сердись is also possible.

Both злиться and сердиться can mean to be angry, but there is often a slight nuance:

• злиться can sound a bit stronger, more like to be mad / angry
• сердиться can sound a bit milder, more like to be annoyed / cross / upset

So:

• Не злись на меня из-за этой ошибки.
• Не сердись на меня из-за этой ошибки.

Both are natural, but злиться may sound slightly stronger emotionally.

The word order can change, because Russian word order is fairly flexible. The original sentence is natural and neutral:

• Не злись на меня из-за этой ошибки.

But you could also hear:

• Из-за этой ошибки не злись на меня.
• На меня не злись из-за этой ошибки.

The meaning stays basically the same, but the emphasis changes:

• putting из-за этой ошибки earlier emphasizes the reason
• putting на меня earlier emphasizes me

For learners, the original order is a very good standard model.

A natural stress pattern is:

• Не злись на менЯ из-за Этой ошИбки.

Notes:

• меня is stressed on the last syllable: менЯ
• этой is stressed on the first syllable: Этой
• ошибки is stressed on и: ошИбки

Also, in fast speech, Russian unstressed vowels are reduced, so the sentence may sound more compressed than an English speaker expects.

A rough pronunciation guide:

• nye zlees' na myNYA iz-ZA EHtay a-SHEEB-kee

That is only approximate, but it can help with first listening and speaking practice.