Hi vaclavkrizek,
Thank you for your purchase.

These strings are in our Label Settings, go to the Settings page and you will see the Label Settings so you can change them there. 

About the string "Please select service" at the moment that is combination of string "Please select" (that you can find in translation strings) and label "service" from Label Settings.

In the latest version we add option Enable Labels Settings in Label Settings of plugin - Disable this option if you want to translate these strings using the third party translation plugin.

You can translate strings with POEDIT and here is an instruction:

1. Download the Amelia plugin from CodeCanyon and save the .zip file on your computer.

2. Unzip downloaded .zip file.

3. You need to download and install POEDIT. 

4. After that open the program and open the file from the extracted folder on your computer ameliabooking/languages/en_US/wpamelia-en_US.po.

5. Translate all the strings on your language.

6. Save the file as it suggests to you (the language code; for example wpamelia-id_ID.po if your language is Indonesian) and it will be generated new  wpamelia-id_ID.mo file. Find your language code here. 

7. Go to ameliabooking/languages/ folder and make new folder and call him as language code for your language (in our case for Indonesian is id_ID) and  then copy these two files called wpamelia-id_ID.po and wpamelia-id_ID.mo and then copy hole folder id_ID back to your website in the location ../wp-content/plugins/ameliabooking/languages/.

Of course, you will use language code for your language (we use Indonesian language and his language code is  id_ID just as example)

When you finish that it would be nice to send us that translation, so we can include in next major update so you don't have to copy this folder from local machine on every update.

Hope this helps If you have any more questions, don't hesitate to ask.

Best regards.