Google Pay does not set any limits for payments by card. The maximum limit of expenses is given by the limit set on the card that you choose in Google Pay service.
In case of transactions up to EUR 20 it is enough to wake up the telephone. In case of transactions over EUR 20 it is necessary to unlock the telephone. Eventually the POS terminal may ask you to unlock the telephone and hold it up it again. Sometimes you may be asked to unlock the screen even in case of transaction up to EUR 20.