Hello,
The codeless slider is tested and it works fine, so its not its problem. I loged in to your site and i saw that you have made many changes on your files related to the sliders: these are causing the malfunction of codeless slider.
Please remove the codes you have added into bootstrap.css and bootstrap-responsive.css.
I found that this line

.header_1.fullwidth_slider_page .top_wrapper {
    padding-top: 150px;
}

is causing the white space above the slider; you can remove this.
Let us know if the issue persist even after you edit the files (you can reply in this topic, don’t need to open other topics).

Best regards!

Hello,

The slider does not have any issue with slider height. Add the % sign if you want to assign the value in percentage or leave just the number, if you want a height in px.

Did you remove the changes you made to theme files? (Please see our latest reply).
If the issue persists, just download a fresh copy of theme files and overwrite the changed files with it.
Let us know.

Best regards!

Hello,
You have an old version of theme. Please update theme to its latest version 2.0. There are so many changes and improvements that we have made, that’s why your codeless slider have issues with the old version.
Let us know if the issue persist even after theme update.
Best regards!

Hello,

You may want to consult your host provider regarding the backup. The message you are getting means you can not read/write data from database.
To update theme you only need to overwrite the current theme files with the newly downloaded package. So to back up your current files, just save wp-content/themes/specular folder in your computer. Or just rename it and then upload the new theme version.
If you want to make a full site backup (content too) then i suggest you use a backup plugin.
Read these useful articles regarding it:

How to Backup Your WordPress Site (Manually or Via Plugins)

https://www.wpbeginner.com/plugins/how-to-create-a-complete-wordpress-backup-for-free-with-backwpup/

Best regards!

Hello,

Yes, just add this code into your page’s custom css box (if you have different sliders in many pages and want different height for each):

#slider-fullwidth {
    height: 600px !important;
    min-height: 600px !important;
}
.codeless_slider_swiper { height: 600px !important;}
.codeless_slider_wrapper { height: 600px !important;}
.codeless-slider-container { height: 600px !important;}
.codeless_slider .swiper-slide {
    height: 600px !important;
}

Result screenshot.

Best regards!