Photovoltaic Tesla surplus charging with Home Assistant

Hello dear community.
I’ve been setting up my Raspberry 4 with HomeAssistant for about 2 weeks. I know Basic, HTML, Turbo Pascal and a little C. Unfortunately, HomeAssistant is far from over, so I’m expecting a little help here.

Initial situation:
PV system on the roof
Tesla in the garage
Electronic meter is already read in real time via an ESP8266 with Tasmota

Goal
I would like to load the excess PV energy into the electric car. For this I don’t want to control the wallbox, but rather regulate the charging power via the Tesla via API

Now my problem:
-MQTT reading in the HA does not work, no matter what I set in the Tasmota / HA
-EVCC has errors in the configuration and does not start
-With Tesla fleet I can’t access my car

Ask:
What would be the correct procedure? I watched videos endlessly. Maybe just too many and not the right ones?

Maybe there is an “ideal track”? - Or to put it another way: how would you proceed?

I would like to thank you in advance for any tips.

Best regards
Beebee