Problem with Czech version after installation English

Hello,
I have problem with Czech version of WP on webside https://www.hlidanimazlicku.cz. In last time, I chose English language version and now when I want to change to Czech language version, all words on top of the browser (Mozilla and Explorer) has big first letter. Only the first letter of the first word should be big in Czech. How can I change it, please? Or how can I delete the instalation of English version? I think, that this is the problem cause my other websides in Czech do not have problem. I have printscreens of the problem if needed. Thank you. Aneta