Я всегда бережно отношусь к книгам, которые мне дают друзья.

In this sentence, относиться к + dative means to treat, to regard, or to handle something in a certain way.

So:

• бережно относиться к книгам = to treat books carefully
• хорошо относиться к людям = to treat people well

This is a very common Russian pattern:

• относиться к кому? / к чему? = to treat / regard whom? / what?

The verb is reflexive in form (относиться), but here you should mostly learn it as a fixed expression:
относиться к + dative.

Because относиться к requires the dative case.

The noun книга changes like this:

• nominative singular: книга
• nominative plural: книги
• dative plural: книгам

So:

• к книгам = toward books / with respect to books

In this sentence, книгам is plural because the speaker is talking about books in general, specifically the books friends give them.

Бережно is an adverb meaning:

• carefully
• with care
• gently
• in a careful way

So бережно отношусь к книгам means something like:

• I treat books carefully
• I take good care of books

It comes from the idea of protecting or preserving something.

A useful comparison:

• бережно = with care, in a way that protects something
• аккуратно = neatly, carefully, tidily

Sometimes both can work, but бережно strongly suggests care and respect.

Которые means which / that and introduces a relative clause.

Here it refers back to книгам:

• книгам, которые мне дают друзья
• the books that my friends give me

So the structure is:

• main clause: Я всегда бережно отношусь к книгам
• relative clause: которые мне дают друзья

Together:
I always treat carefully the books that my friends give me.

More natural English:
I always treat with care the books my friends give me.

Because it matches книгам in number and gender, and its case depends on its role inside the relative clause.

Here:

• книгам = plural
• so the pronoun must also be plural: которые

Inside the relative clause, которые is the direct object of дают:

• друзья дают что? → которые (the books which friends give me)

That means it is in the accusative plural. But for inanimate plural nouns/pronouns, accusative plural looks the same as nominative plural, so you get которые.

That is why the form is которые, not something else.

Because дать means to give, and the person receiving something is normally in the dative case.

So:

• друзья дают мне книги
• my friends give me books

Here:

• друзья = subject, nominative
• мне = indirect object, dative, to me
• которые = direct object, which / that

This is a very common pattern:

• дать кому? что?
• to give someone something

Yes, it is grammatically present tense, but in Russian the present tense often expresses habitual or repeated actions, just like in English.

So:

• друзья дают мне книги can mean my friends give me books
• not necessarily right now at this exact moment

Likewise:

• Я всегда бережно отношусь... = I always treat... carefully

The whole sentence describes a general habit or repeated situation, not a single event.

Because the sentence is about a repeated / regular action, not one completed act.

• давать = imperfective, to give in a repeated, ongoing, or general sense
• дать = perfective, to give once, as a completed act

Here the meaning is:

• the books that my friends give me in general
• not the books that my friends once gave me

So imperfective дают is exactly what you would expect.

Because in Russian, a relative clause introduced by который is normally separated by a comma.

So:

• книгам, которые мне дают друзья

This is standard Russian punctuation, even where English might sometimes be less strict.

The comma marks the beginning of the clause which my friends give me.

Russian word order is more flexible than English word order. Both are possible:

• которые мне дают друзья
• которые друзья дают мне

In this sentence, которые мне дают друзья sounds natural and smooth. It can put a little more focus on мне before revealing the subject друзья.

A rough breakdown:

• которые = which / that
• мне = to me
• дают = give
• друзья = friends

Even though the order differs from English, the cases make the roles clear:

• мне is dative → recipient
• друзья is nominative plural → subject

Yes, often it could be.

Russian often drops subject pronouns when the verb ending already shows who the subject is:

• Я отношусь → отношусь already means I treat / I relate

So you could say:

• Всегда бережно отношусь к книгам, которые мне дают друзья.

That would still be correct.

Including Я can make the sentence:

• a bit clearer in isolation
• slightly more emphatic
• more natural in some contexts, especially for learners or when contrasting with someone else

It strongly suggests that idea, but it does not literally say borrowed.

The sentence says:

• the books that my friends give me

Depending on context, that could mean:

• books they lend me
• books they hand me
• books they give me as gifts

However, because of бережно отношусь к книгам and the mention of friends giving them to the speaker, many people will naturally understand it as books my friends lend me or entrust to me.

If you wanted to make lend explicit, Russian would more likely use дают почитать or одалживают in the right context.

Всегда means always, and its position here is very normal:

• Я всегда бережно отношусь...

It comes before the verb phrase and modifies the whole statement:
I always treat books carefully...

Russian allows some movement for emphasis, but this order is neutral and common.

For example:

• Я всегда бережно отношусь к книгам... = neutral
• Я бережно всегда отношусь... = much less natural
• Всегда я бережно отношусь... = possible, but more marked or emphatic

So the sentence uses the most standard placement.

Grammatically you can see how the pieces line up that way, but it is not good English.

A more natural translation is:

• I treat books carefully
• I handle books with care
• I take good care of books

This is a good example of where you should translate the whole expression, not each word separately:

• бережно относиться к чему-либо = to treat something with care