Biovars (dismo package) with data from DWD

Question

I am new to R and I tried to calculate the bioclimatic variables with the biovars function from the dismo package for weather data from the DWD (Deutscher Wetterdienst). I need those variables for specific inventory plots, and so my first idea was to extract the monthly precipitation and temperature min and max for each inventory plot, and then calculate the bioclimatic variables for each plot. My output of this process is a data frame, which is not useable as input for biovars. Now I am struggling to get a valid input format for the biovars function (vector, matrix, RasterStack) either out of this data frame or with the original data from DWD (and then extract the plots later).

This is my script for the min temperature per month:

index <- indexFTP(folder="monthly/air_temperature_min", base=gridbase)
index <- index[-(1471:1472)] # exclude description files, monthly at the end of the list
index <- index[as.numeric(substr(index,71,76)) >=201001] # after year 2010/01
index

# download & read data:
tempminM <- dataDWD(index, base=gridbase, joinbf=TRUE)
names(tempminM) <- substr(names(tempminM), 71, 76)

# terra raster:
tempminM_stack <- terra::rast(tempminM)
crs(tempminM_stack) <- "+proj=tmerc +lat_0=0 +lon_0=12 +k=1 +x_0=4500000 +y_0=0 +ellps=bessel +units=m +no_defs"

# Extract values
tempminM_pred <- extract(tempminM_stack, sf_coord_plots_gk3)
tempminM_pred <- cbind(tempminM_pred, sf_coord_plots_gk3)

`

tempminM is a list. tempminM_stack is a SpatRaster

I tried to get a Rasterstack from the tempminM_stack , but it's all NA.

# to stack
tempminM_stack_stack <- terra::as.raster(tempminM_stack)
tempminM_stack_stack <- as.matrix(tempminM_stack_stack)

I would be very happy to get a hint! Thanks a lot!