Je lis les conditions de retour pendant le délai de rétractation.

Because lis is the 1st person singular present tense of the verb lire (to read).

Conjugation in the present:

• je lis — I read / I am reading
• tu lis — you read
• il/elle/on lit — he/she/one reads
• nous lisons — we read
• vous lisez — you read
• ils/elles lisent — they read

So lire is the infinitive (to read), while lis is the form that matches je.

It can mean either one, depending on context.

French often uses the simple present where English might use:

• I read
• I am reading

So Je lis les conditions de retour... can naturally mean:

• I read the return conditions...
• I am reading the return conditions...

If French wants to emphasize the ongoing action, it can say:

• Je suis en train de lire... — I am in the middle of reading...

But in many everyday situations, Je lis is enough.

Les is the definite article: the.
Des is usually some or plural indefinite a/an.

Here, the sentence refers to specific conditions — the return conditions/policy relevant to a purchase or situation. That is why French uses les:

• les conditions = the conditions
• des conditions = some conditions

So les conditions de retour means the return conditions or the return policy/terms.

Because French often talks about rules, terms, or requirements in the plural:

• les conditions = the conditions / terms
• les conditions de vente = terms of sale
• les conditions d’utilisation = terms of use

Even if English might sometimes prefer something like return policy in the singular, French commonly uses conditions in the plural to refer to the set of rules or terms.

Here, de retour means for return(s) or about returns.

So:

• les conditions de retour = the return conditions
• more literally: the conditions of return

This is a very common French pattern:

• nom + de + nom

Examples:

• un billet de train — a train ticket
• une salle de bain — a bathroom
• les conditions de retour — return conditions

Also, retour here is a noun (return), not the verb retourner.

Because de is very commonly used to link two nouns in French.

It often corresponds to English structures like:

• of
• sometimes a noun used like an adjective
• sometimes a compound noun

In this sentence:

• conditions de retour = conditions for/of return
• délai de rétractation = period of withdrawal / cancellation period

French uses de in many places where English simply puts two nouns together:

• car door → porte de voiture
• return policy → conditions de retour

So the repeated de is completely normal.

Pendant means during.

So:

• pendant le délai de rétractation = during the withdrawal period

It places the action inside a span of time.

A helpful comparison:

• pendant = during
• après = after
• avant = before

Example:

• Je lis pendant la pause. — I read during the break.

Possibly, but the meaning changes a bit.

• pendant le délai de rétractation = during the withdrawal period
• dans le délai de rétractation often suggests within the withdrawal period / before it ends

So:

• pendant focuses on the action happening during that time span
• dans can suggest staying inside a deadline or time limit

In legal or administrative contexts, both may appear, but they are not exactly the same.

This is a set legal/consumer phrase.

• délai = period, time limit, deadline
• rétractation = withdrawal, cancellation of a purchase/contract within a legal period

So le délai de rétractation is the period during which a customer is allowed to change their mind and cancel or return something, depending on the rules.

In natural English, this may be translated as:

• the withdrawal period
• the cooling-off period
• sometimes the return period, depending on context

Because délai is a singular countable noun here, and French normally needs an article before such nouns.

So:

• le délai = the period / the deadline

French generally does not omit articles as often as English does.
Compare:

• during the period → pendant le délai
• not usually just pendant délai

The article is required here.

Not especially in casual everyday speech. It is more common in:

• legal language
• administrative language
• online shopping/customer service contexts

A learner may see it in things like:

• return policies
• contract terms
• e-commerce websites

So it is a useful word, but it sounds more formal and technical than very basic daily vocabulary.