1. Album Descriptions
My album descriptions sometimes get a tad lenghthy... to lengthy for to the right and a line or two below the album in the albumlist... this is fine, it auto cuts off with a "[...]"

BUT id like to somewhere be able to see the full descrtiption... (the part the [...] seems to be not readable anywhere...), preferably Id like to have this (the full descritpion then) either above the pictures when clicking the album or below the pictures (so on the overview list of all the foto's in the album)

This point has been on my todo list for a long time now, but I currently don't have time to work on this right now...
Since you proposed to modified your tpl, Maybe the easiest way is to alter the line

<p>{$cat.DESCRIPTION|truncate:200:" [...]"}</p>

in the mainpage_categories.tpl

2. Picture navigation
Maybe I accidentely broke something but I cannot move from one picture to the next withour returning to the album.. there are no "arrows" left and right of the pictures themselves :(

You need to tell us more if you want some help here ... Maybe the arrow keys of your keyboard still do the trick.

3. Catgagories - Subalbums font difference
When clicking on a catagorie it opens op the albumlist on the left side (with the amount of pictures to the right of that that are present in the album). This is fine, however, how can I change the fontsize of the catagories so that the "indent" difference isn't the only way to see the difference between the content of the catagorie and the catagorie name itself ? Id like my main catagories to be a little "bigger" font then the indented subalbums so that's it's not one "block of same style text" and thus easier to glance :)

This is actualy a good idea, and I'll add it to my todo list ! But, as stated before, it may take a while for a release...  In the mean time, you can probably add something like this to the css

#menubar ul li ul {
  font-size:80%;
}

in the LocalFile Editor plugin.

Ok clean slate, some more questions...

1. You gave me code to make the subalbums "smaller" compared to the main catagories. What's the code to do the following:
- Make the main catagories bigger (leave the subalbums at their current size)
- Add one whiteline between the catagories (but not between the catagorie and it's subalbums)

2. I forgot to activate the arrows in my settings to navigate between pictures :( so that was easily fixed, however.. to have the arrows "appear" you need to move your cursor outside of the picture in the white border left or right respectivly... how can I make it so the arrows appear from about 1cm either side already ?

Thanks for the help!