It's a bit early to tell for sure especially with the one on the left (they are both different plants). The one on the right looks like purslane (Portulaca oleracea. The one on the left could be a pigweed (Amaranthus) or nightshade (Solanum) or something else. I think purslane has a wide enough distribution to occur in Slovakia but I don't know what possibilities grow there for the seedling on the left.
I'm going to suggest your question be moved over to the Plant ID forum, there may be someone there that knows what grows in Slovakia.