The wood burning stove is intended for intermittent combustion. This means that the stove will burn properly with a small amount of wood fuel, typically lasting 1-2 hours (it can go up to 4-5 hours), provided that there is sufficient air supply, that flue gasses are released, and that the wood is allowed to burn down to embers before more is loaded in.
 
If the door is opened while there are visible flames, a large influx of cold air will be sucked into the combustion chamber, which may stir up ash and cause smoke problems. You should therefore always wait until the wood has burnt down into embers without visible flame before loading new wood.

If you nonetheless need to open the door before the wood has burnt down to embers, the door can be opened approx. 1-2cm for 10-20 seconds or the primary damper for approx. 1-2 minutes. This will result in increased draw through the stove and thereby reduce the risk of fly ash and smoke problems.

The problem might also be the chimney

If there is inadequate draft in the chimney (low chimney draft), the smoke will always find the most immediate route of escape, such as through the door or the chimney cowl.

Note that low chimney draw is often seen in well-sealed houses or with powerful kitchen ventilation hoods or exhaust systems, as these can create negative pressure in the space around the wood burning stove. This can result in smoke problems and a poor combustion. In this case, it will be necessary to open a window to supply air for combustion and thereby equalize the negative pressure.