There are a few different ways how you can top up myTU account.
You can add your credit or debit card information - just like a simple payment, you will be able to add a selected sum whenever it is necessary.
The minimal limit for a single top up is 5 EUR. The maximum limit is 1000 EUR. There is no monthly limit, however, if high sums are being added, the account is subject to investigation by the KYC team.
You can send a request to your fellow myTU users by using the option in "Add Money". The transactions should be reflected in your balance immediately.