Construction costs are currently skyrocketing

Wastewater is not on the invoice at all

Wastewater is paid through the property charges, so it comes separately or with a delay.

Sewage is paid through property taxes, so it comes separately or with a delay.

Not necessarily with a delay. But with a separate invoice.
For us, these are also two different companies. Interestingly, one comes as a notification, the other as an invoice. So they also have different legal forms.

The four of us consume about 80 cubic meters of water per year and pay 99€ every 2 months for it.

Here it was first increased to 1.50 per cubic meter, wastewater 2.20 but last time 9 years ago... I think that is okay

Not necessarily delayed. But with a separate invoice.
For us, these are also two different companies. Coincidentally, one comes as a notice, the other as an invoice. So they also have different legal forms.

Yes, one is a fee and therefore comes as a notice, and the other is simply a consumption invoice.
With us, the fee must always be paid at certain dates during the year (I think 4 or 5 dates) or it will be collected if a direct debit authorization has been given. The dates are published on the municipality’s homepage and in the newspaper (they might also generally be noted on the notice, I am not sure about that right now). The first one is now, for example, at the end of February.

Interesting, with us water and wastewater are managed by the water association in a single annual billing and both depend on the volume.