Keycloak behind IIS Reverse Proxy - iis

Question

I just cant get my reverse proxy to work properly and I hope that someone can help me with that.
A few Informations:
1 VM Windows Server 2019,IIS 10 (with ARR and URL Rewrite Module),"keycloak" App under the "Default Website", proxy-address-forwarding="true" were added in the standalone.xml
keycloak is locally available at "localhost:8080". The default website is available from intern network (Port 80 is open, 8080 is closed). I want to use the IIS as a reverse proxy for keycloak. It should look like the following URL.
Request: "http://server_fqdn/keycloak" -> IIS Reverse Proxy -> localhost:8080
At first I tried it without "/keycloak" and it worked perfectly. After I added "/keycloak" it just shows 404 Errors. I saw that it tries to open "http://server_fqdn/auth" instead of "http://server_fqdn/keycloak/auth". If I enter "/keycloak/auth" manually it works. My first thought was to just write another Blank Inbound Rule which redirects "http://server_fqdn/auth" to "http://server_fqdn/keycloak/auth". It works, but now there is another problem. If i want to enter the admin console I get an error which says "Invalid parameter: redirect_uri".
It stops at the following URL (not complete, but the necessary part is there)
http://server_fqdn/keycloak/auth/realms/master/protocol/openid-connect/auth?client_id=security-admin-console&redirect_uri=http%3A%2F%2Fserver_fqdn%2Fkeycloak%2Fauth%2Fadmin%2Fmaster%2Fconsole%2F&state=.....
If i remove %2Fkeycloak after "redirect_uri" it works and i get the keycloak login screen. Maybe someone can help me here.
Inbound Reverse Proxy Rule:
<rule name="ReverseProxyInboundRule1" enabled="true" stopProcessing="true">
<match url="^keycloak/(.*)" />
<conditions logicalGrouping="MatchAll" trackAllCaptures="false" />
<action type="Rewrite" url="http://localhost:8080/{R:1}" />
<serverVariables>
</serverVariables>
</rule>
Outbound Reverse Proxy Rule:
<outboundRules>
<clear />
<rule name="ReverseProxyOutboundRule1" preCondition="ResponseIsHtml1" enabled="true">
<match filterByTags="A, Area, Base, Form, Head, IFrame, Img, Input, Link, Script" pattern="^http://localhost:8080/(.*)" />
<conditions logicalGrouping="MatchAll" trackAllCaptures="true">
</conditions>
<action type="Rewrite" value="http://server_fqdn/keycloak/{R:1}" />
</rule>
<preConditions>
<preCondition name="ResponseIsHtml1">
<add input="{RESPONSE_CONTENT_TYPE}" pattern="^text/html" />
</preCondition>
</preConditions>
</outboundRules>
Inbound Reverse Proxy Rule:
<rule name="keycloak" enabled="true" stopProcessing="true">
<match url="^auth/(.*)" />
<conditions logicalGrouping="MatchAll" trackAllCaptures="false" />
<action type="Redirect" url="http://server_fqdn/keycloak/{R:0}" redirectType="Permanent" />
</rule>