Since yesterday I take Zotral 50mg and I feel very bad (I have tense muscles and increased pressure, I can not sleep and I have problems walking) - is this normal at the beginning of treatment?

Yes, at the beginning of the treatment there may be side effects such as restlessness, increased tension, agitation, deterioration of mood - therefore, you should start the treatment with the lowest possible doses and gradually increase the amount of the drug until the therapeutic dose is reached. Usually, these symptoms disappear spontaneously within about two weeks of starting treatment. After this time, you can usually see the effect of Zotral (although sometimes you have to wait up to 4 weeks to get a full improvement). If the initial side effects worsen the quality of life, it is worth visiting a psychiatrist for additional supportive drugs (e.g. calming or facilitating falling asleep). I recommend the article: https://www.gdziepolek.pl/artykuly/jak-poradzic-sobie-z-nerwica