I found a solution. The bellow wpml-config.xml does the trick. It should be copied to the theme root directory.
<wpml-config>
<admin-texts>
<key name="thinkup_redux_variables">
<key name="thinkup_homepage_sliderpreset">
<key name="0">
<key name="slide_title" />
<key name="slide_description" />
<key name="slide_url" />
</key>
<key name="1">
<key name="slide_title" />
<key name="slide_description" />
<key name="slide_url" />
</key>
<key name="2">
<key name="slide_title" />
<key name="slide_description" />
<key name="slide_url" />
</key>
</key>
<key name="thinkup_general_sitetitle" />
<key name="thinkup_general_sitedescription" />
<key name="thinkup_homepage_section1_title" />
<key name="thinkup_homepage_section1_desc" />
<key name="thinkup_homepage_section2_title" />
<key name="thinkup_homepage_section2_desc" />
<key name="thinkup_homepage_section3_title" />
<key name="thinkup_homepage_section3_desc" />
</key>
</admin-texts>
</wpml-config>