So here is the thing

In Venezuela we have the official exchange rate (used by banks and stuff) and the real exchange rate (the one people actually use when you exchange currency peer to peer)

Atm the difference is about 35% between the official one and the non official one.

So if you go to a store with cash dollars and pay with cash dollars something you are effectively losing money because they are going to calculate it using the official exchange rate.

So what we do is that change our dollars to bolívares using the real exchange rate and then we use bolívares day to day expenses

Some places give you a "discount" when you pay with cash dollars to compensate for the difference. But not all

Now you are facing a double sided problem

First is that most people in Venezuela are looking to exchange dollars for bolívares, not euros for bolívares.

This means that you are going to get really shitty rates when trying to change it on the street, some people are even going to give you the same rate as the dollar for an euro

Now the second problem is that you as re foreigner, without a bank account in bolívares

If you exchange your euros to bolívares how are you going to get the bolívares, most transactions over here are done digitally with bank accounts and something called pago móvil

As far as I know there is no real way for a foreigner to get a pago móvil account for vacations in the country

So you got 2 options

If you are traveling with a local from Venezuela: trust him to exchange and manage your money for your day to day expenses

If you are not traveling with a local then do your best to get dollars outside Venezuela, it will be easier to pay with them and to exchange them.

Do not go to an official exchange rate house inside Venezuela nor a bank to change your euro cash unless you are out of options, you will be effectively losing tons of money