HTTP Binding OH3

Hi there,
I have the following problem.
I switched from OH2.5 to 3 and now the HTTP binding has changed.
I would like to access my Comexio heating control from OH3 and read status queries and make settings via OH3.
The Comexio server accepts requests that have to be structured as follows:

The marker M35 is read here.

To write:
Here the flag is assigned the status “1”.

How can you best solve this with the new binding?

Reading goes. For this I have created a thing:

Thing http:url:Comexio_abfragen “Comexio abfragen” [ baseURL=“”, refresch=30, timeout=3000, commandMethod=“GET”, delay=1000] {
Type number : Speicher_oben [ stateExtension=“api/?action=get&marker=M1”, commandExtension=“REGEX(.)"]
Type number : Speicher_Bereitschaft [ stateExtension=“api/?action=get&marker=M2”, commandExtension="REGEX(.
Type number : abfrage_PV_Freigabe [ stateExtension=“api/?action=get&marker=M53”, commandExtension=“REGEX(.)"]
Type number : abfrage_PV_ein [ stateExtension=“api/?action=get&marker=M157”, commandExtension="REGEX(.

and under Items the following item:

Number Heizung_Speicher_oben “Oben [%.1f °C]” {channel=“http:url:Comexio_abfragen:Speicher_oben” }
Number Heizung_Speicher_Bereitschaft “Bereitschaft [%.1f °C]” {channel=“http:url:Comexio_abfragen:Speicher_Bereitschaft”}
Number Heizung_abfrage_PV_Freigabe “PV Heizung Freigabe [%f]” {channel=“http:url:Comexio_abfragen:abfrage_PV_Freigabe”}
Number Heizung_abfrage_PV_ein “PV Heizung ein [%f]” {channel="http:url:Comexio_abfragen:abfrage_PV_ein "}

But how do I write back my own values?
My test doesn’t work:

Thing http:url:Comexio_steuern “Comexio steuern” [ baseURL=“”, commandMethod=“PUT”, delay=1000] {
Type string : HZ_Vorlauf_Pumpe_send [ stateContent=“api/?action=set&marker=M49”, onValue= “&value=1”, offValue= “&value=0”]
Type string : HZ_PV_send [ stateContent=“api/?action=set&marker=M53”, onValue= “&value=1”, offValue= “&value=0”]

Switch HZ_Vorlauf_Pumpe “Vorlaufpumpe” (gHeizung_alle) {channel=“http:url:Comexio_steuern:HZ_Vorlauf_Pump e_send”}
Switch HZ_PV “PV Heizung Freigabe” (gHeizung_alle) {channel=“http:url:Comexio_steuern:HZ_PV_send”}

Could someone give me a tip?

Thank you very much