accessibility of my website / editing in wordpress application

hi everyone,

I am new in establishing a website, so I thought for my requirements a wordpress blog would be the best and “easier” to setup.

I was looking for a template that fits basically my taste.
Before adapting, my website with the template was always only partly seen (some pics were missing in the category-tree on the top).

I adapted (until now the category titles and pics – which clearly have a smaller size than the original ones) the site.

First of all if I go on my website, there is
a) every time only a part of the category pics visible
or
b) even the whole design not loaded (all the infos are visible, but no design)

and the site does need very long to load, although there are no any infos yet online

is this a problem caused by wordpress or my provider?

then, I do have another problem, so I am not able to continue my site-building:

if I log in the wordpress editor, I first see the main surface. If I click on any button (eg. Apperance or Post) there is no reaction.
it loads, but I don’t get in the subcategory – just repeats to show the main category. rarely I get in a subcategory, but finally stucks there and loads the same view although I try to click some other option-buttons.

my website’s adress is https://www.deelight.at (or deelight.at)

can anybody pleaaaaseee help me?
I am really depressed not to continue working on my website. It doesn’t make fun, if you are not able to see/edit your page….

thank you very much in advance!

dee