Если я не высплюсь, мне трудно сосредоточиться и не хочется говорить.

It comes from the verb выспаться, which means to get enough sleep / to sleep enough to feel rested.

So Если я не высплюсь... means:

• If I don't get enough sleep...
• If I don't sleep enough...

It is not just sleep in general. It specifically means sleep sufficiently.

The ending -ся / -сь is the reflexive marker.

In this verb, it is just part of the normal dictionary form выспаться. It does not mean a literal English myself. Instead, it helps form a verb meaning something like:

• to sleep oneself into a rested state
• to get enough sleep

Russian has many verbs where -ся creates a meaning that is natural in Russian but not translated literally into English.

Because выспаться is a perfective verb, and perfective verbs in Russian do not have a present tense. Their non-past forms are interpreted as future.

So:

• высплюсь = I will get enough sleep
• не высплюсь = I will not get enough sleep

After если, Russian often uses this future form where English uses a present tense:

• Если я не высплюсь...
• If I don't get enough sleep...

This is completely normal Russian grammar.

Yes, but the meaning changes.

• Если я не высплюсь = if I don't get enough sleep on a particular occasion, or in any future case
• Если я не высыпаюсь = if I'm not getting enough sleep regularly / habitually / these days

So the sentence you have sounds like:

• If I don't get enough sleep, ...

while не высыпаюсь would sound more like:

• If I’m not getting enough sleep, ...
• When I’m sleep-deprived over time, ...

Because Russian often uses the dative case to show the person who experiences a feeling or state.

So:

• мне трудно literally = to me, it is difficult
• natural English = it is hard for me

This pattern is very common in Russian:

• мне трудно = it’s hard for me
• мне легко = it’s easy for me
• мне холодно = I’m cold
• мне хочется = I feel like...

So я трудно is not correct here.

Here трудно is not just a regular adverb meaning with difficulty. It is being used as a predicative word: a word that expresses a state or condition.

So in мне трудно сосредоточиться, it means:

• it is hard for me to concentrate

This is a very common Russian structure:

• кому? + трудно / легко / нужно / можно + infinitive

For example:

• Мне трудно понять. = It is hard for me to understand.
• Ему легко работать. = It is easy for him to work.

Because after трудно, Russian normally uses an infinitive:

• мне трудно сосредоточиться
• it is hard for me to concentrate

This is the standard pattern:

• трудно + infinitive
• легко + infinitive
• приятно + infinitive
• невозможно + infinitive

You could express a similar idea in other ways, such as Я не могу сосредоточиться, but that is a slightly different structure and can sound stronger: I can't concentrate rather than it's hard for me to concentrate.

Russian often prefers the perfective infinitive here because the idea is to manage to get focused, to achieve concentration.

So трудно сосредоточиться means something like:

• it’s hard to focus
• it’s hard to get myself concentrated

The imperfective counterpart would suggest more of an ongoing process and is less natural in this sentence.

So for a learner, трудно сосредоточиться is the normal phrase to remember.

These are similar, but not identical.

• мне не хочется говорить = I don't feel like talking
• я не хочу говорить = I don't want to talk

The version with хочется is:

• more impersonal
• softer
• often about a temporary mood or feeling

So in this sentence, не хочется говорить fits very naturally: after not getting enough sleep, the speaker is describing a state they experience, not making a firm decision or refusal.

Because it is understood from the first part.

The full version could be:

• Если я не высплюсь, мне трудно сосредоточиться и мне не хочется говорить.

But Russian often leaves out repeated words when the meaning is already clear.

So the sentence means:

• If I don't get enough sleep, it’s hard for me to concentrate and I don’t feel like talking.

The мне applies to both:

• мне трудно сосредоточиться
• (мне) не хочется говорить

Because говорить means to talk / to speak as an ongoing or general activity, while сказать means to say something once, as a single completed act.

Here the meaning is:

• I don't feel like talking

So говорить is the natural choice.

Compare:

• не хочется говорить = I don’t feel like talking
• не хочется ничего сказать = I don’t feel like saying anything

In your sentence, the idea is the general activity of speaking, not one specific utterance.

Yes, Russian word order is flexible, but the original sentence is a very natural neutral version:

• Если я не высплюсь, мне трудно сосредоточиться и не хочется говорить.

You may see variations for emphasis, but for learning purposes, this version is the safest model.

For example, Russian can move parts around to highlight different information, but that usually adds a nuance of emphasis or style. So unless you have a special reason, keep the original order.