Telegraf, MQTT and value reading

I have a device, sending several data over MQTT under 1 main topic and several subtopics.

P1/highest_peak_pwr_ts = 240204154500W
P1/energy_delivered_tariff1 = 2078.767
P1/energy_delivered_tariff2 = 2829.133

I use folowing config:
servers = [“tcp://”]
topics = [

data_format = “value”
data_type = “float”

measurement = “mqtt_consumer”
dest = “P1Meter”
data_format = “value”
data_type = “float”

When I look into the database, I see the “_field” which is always “value”. When I do a rename of this, and when I do that in 2 different mqtt_consumer_parsing statements, the second is ignored, I can only get 1 name in the field.
In the _field I would like things like “tariff1”, and “tarrif2”, etc… Tried 3 miljon times with a lot of different things, no joy however.

How to convert and use the mqtt field P1/highest_peak_pwr_ts = 240204154500W
This is a timestamp but I have no clue how to convert it and use it.