EPSG:4326 does not convert nicely into meters, but you can calculate the lengths of latitude and longitude degrees for example with
At 54°N the length of latitude is 111304.96 m and length of longitude is 65575.75 m.
Your BBOX is 0.1537 degrees high and 0.1977 degrees wide.
HEIGHT = 0.1537 / (1/111304.96) = 17107.57235
WIDTH = 0.1977 / (1/65575.75) = 12964.32578
However, if you really want to have resolution in meters, use some projected coordinate system instead of EPSG:4326. For example UTM zone 35N should be good for Poland http://epsg.io/32635.