In this situation, are you allowed to use the surface on the left side to park the vehicle?

On the left side of the roadway you can see an area covered with white diagonal lines, bordered by a solid line. This is marking P-21 "hatched area". Such an area is neither a traffic lane nor a parking space - entering it and stopping on it are prohibited, so you must not use it for parking.

The Regulation on road signs and signals says that marking P-21 means an area of the road where entering and stopping are prohibited. Hatched areas are painted where lanes split and merge, before traffic islands and at junction approaches, to organise the paths of vehicles. Treat them like an island: you go around them and do not drive onto them.

Legal basis: § 90 para. 5 of the Regulation on road signs and signals