The best place to transplant them to would be the ground. They are quite tolerant of repotting, so if they are still alive I imagine they would survive transplanting. But they are much easier to grow in the ground than in pots. These kinds of bamboo naturally grow in places with a severe winter (eg, mountains in the interior of China) and so are typically hardy to below -20C. So (guessing you are in Lithuania) I imagine they would do well outdoors even in Vilnius, provided the growing season is long enough. In a pot, it is more difficult to overwinter them, since in a pot the roots can get much colder than they would in the ground. Also water transport continues in the ground in the winter, but in a pot the frozen outer layer can hinder water transport, leaving the bamboo to die of drought.

Like the others, I think that your main problem is either underwatering or waterlogging, it is difficult to tell which since the symptoms are similar. From the pictures, I see someting that looks lika about an 80cm cube, if that is the container then that is a good size/shape for growing containerised bamboo. They need drainage holes (another good reason this is difficult indoors given the quantity of water you will need, and the amount that will drain out of the bottom) and a well-drained but water-retentive medium, eg, a mix of compost and garden soil (not heavy clay), with some added sand and grit for improved drainage if necessary.

Cultivation of hardy bamboos in a indoor environment suited to human habitation is likely to be difficult. Apart from the logistical problems of watering and draining a container probably weighing several hundred kg, the environment will be insufficiently humid, and the plants would like to have a winter.