natrualHazards <- readOGR(dsn= "pathto.gpkg", "WB_SYN_GK_F") # readOGR
natrualHazards <- st_read(dsn= "pathto.gpkg", layer = "WB_SYN_GK_F") # st_read

pgInsert(con, name=c("public",paste(c("tablename"),collapse="")),
     naturalHazards,
     geom = "geom", df.mode = FALSE,
     overwrite = TRUE,
     df.geom = c("geom",paste(c("(MultiPolygon,2056)"),collapse="")), geog = FALSE)

landuse <- readOGR(dsn= fgdb, "Bodenbedeckung_BoFlaeche_Area") # readOGR

landuse <- st_read(dsn= "pathto.gpkg", layer = "Bodenbedeckung_BoFlaeche_Area) # st_read

conn = dbConnect(PostgreSQL(), dbname = "dbname", user= "postgres", password = "password", host = "localhost", port = 5432)
st_write_db(conn, landuse , drop=TRUE)

landuse_sp <- as(landuse, "Spatial")