If your employer matches your contribution, then you should contribute as much as is allowed. In other words, if they contribute €3,000 because you contribute €3,000, then you should contribute €3,000. If they contribute 10% whether or not you contribute, then the following applies:
You should not contribute to a pension unless you are getting the full tax relief on it.
But you should save the money which you would have contributed.
I would go further and say that you should not contribute to a pension scheme at all until you have saved up the deposit to buy a house. That is the most financially efficient and tax effective way of saving. When you have bought a home and got your mortgage down to a comfortable level, then contribute to a pension.
Brendan