Depo teslim formunu imzalamadan önce kiralık depoyu incelemiş olmanız lazım.

It means before signing.

It is built like this:

• imzalamak = to sign
• imzalama- = signing
• -madan / -meden = without doing / before doing in this kind of structure
• önce = before

So:

• imzalamadan önce = before signing

A very literal breakdown is something like before not-signing-yet, but in normal Turkish this is just the standard way to say before doing something.

Because incelemiş olmanız lazım adds the idea of completion before another action.

Compare:

• incelemeniz lazım = you need to inspect
• incelemiş olmanız lazım = you need to have inspected

In this sentence, the inspection must already be finished before the form is signed. That is why Turkish uses the more complete-looking structure.

So the sentence is not just saying inspection is necessary. It is saying the inspection should already have been done by that point.

Here, -miş is not mainly about hearsay or reported information.

In incelemiş olmanız, it helps create a perfect/anterior meaning:

• incelemiş olmak = to have inspected

So in this sentence, -miş is part of the idea have done something already, not necessarily apparently or I heard that.

This is a very common point of confusion because -miş can do different jobs in Turkish depending on the structure.

Because Turkish often leaves the subject unstated when it is already clear from the endings.

Here, olmanız contains the person marker:

• -nız / -niz / -nuz / -nüz can refer to you plural
• it can also be used as a polite singular you

So Turkish does not need to add siz unless it wants extra emphasis or contrast.

In other words, the idea of you is already built into olmanız.

olmanız is part of a nominalized clause.

The structure is:

• incelemiş olmanız = your having inspected / that you have inspected

Turkish often turns whole actions into noun-like units. English usually prefers a full clause such as that you have inspected or an infinitive-like expression such as to have inspected.

So:

• incelemiş olmanız lazım literally means something like
  your having inspected is necessary

Natural English, of course, is:

• you need to have inspected

Because formunu is the definite direct object form of depo teslim formu.

First, notice that depo teslim formu is a noun compound:

• form = form
• formu = the compound form of form in this phrase

Then, because it is the specific thing being signed, it takes the accusative ending.

So:

• depo teslim formu = the warehouse handover form
• depo teslim formunu = the warehouse handover form as a specific object

The extra n is a buffer consonant that appears between endings.

For the same general reason: depoyu is a definite direct object.

• depo = warehouse
• depoyu = the warehouse

In Turkish, specific direct objects usually take the accusative ending:

• depoyu incelemek = to inspect the warehouse
• bir depo incelemek = to inspect a warehouse

So kiralık depoyu incelemiş means having inspected the rental/rented warehouse, not just having inspected some warehouse.

kiralık is an adjective meaning something like:

• for rent
• rental
• sometimes, depending on context, rented

It comes from kira (rent) plus a suffix that makes it into an adjective-like form.

So:

• kiralık depo = rental warehouse, warehouse for rent, or in context the warehouse being rented

The exact best English wording depends on the situation, but grammatically it is simply an adjective modifying depo.

This is a very common Turkish noun-compound pattern.

• depo = warehouse
• teslim = delivery / handover
• formu = form

Together:

• depo teslim formu = warehouse handover form

Turkish often puts nouns together where English might use:

• a compound noun
• an of phrase
• or an adjective + noun phrase

So instead of something long like the form for the handover of the warehouse, Turkish can package it compactly as depo teslim formu.

Turkish normally puts the main predicate at the end, so the sentence is arranged very differently from English.

A rough structure is:

• Depo teslim formunu imzalamadan önce = before signing the warehouse handover form
• kiralık depoyu = the rental/rented warehouse
• incelemiş olmanız lazım = you need to have inspected

So the overall order is roughly:

• Before signing the form, the warehouse, you need to have inspected

That sounds unnatural in English, but it is normal Turkish word order.

Yes. A fairly literal version would be:

• Before signing the warehouse handover form, it is necessary that you have inspected the rental warehouse.

That helps show the grammar:

• imzalamadan önce = before signing
• kiralık depoyu = the rental warehouse
• incelemiş olmanız = your having inspected
• lazım = necessary

Natural English would usually be:

• You need to have inspected the rental warehouse before signing the warehouse handover form.

Both reflect the same Turkish sentence; one is just more literal and the other more natural.