Gave one of the daily ones a try on Friday night (1 of 2, Buildings or however it's called) and gotta say it was tough for me (even though it was only 6x6 in size) and I hadn't solved anything like that before.
Most Skyscraper puzzles are 6x6 -- it doesn't tell you much of anything about the difficulty level of the puzzle.
In fact, since the median time on that one was around 7-8 minutes, I'd say it was a reasonably hard puzzle.
Also, just getting through your first puzzle of a given type is a good start.
In general, for Skyscrapers, I'd recommend starting by figuring out where the 6's and 5's have to be if possible.
Also a couple general interface notes that help on a lot of puzzles (including hard skyscrapers), in case you hadn't tried them out yet:
1) hitting # toggles "candidate" or "pencil marks" mode, where you can list possibilities. I find this handy in skyscrapers, kropkis, and sudokus especially.
2) The puzzles can be done in "layers" -- if you look on the app where there's a "Stufe: 0" and a "+", you can branch/bifurcate your solution if needed.
For example, suppose you realize that there are two basic ways the 5 can go in a certain row. Click the "+" to switch the layer to "1" and try it one way. If it works, great. If not, click back
to "0" (by hitting "-") and the puzzle reverts to where you branched (and you can put the 5 in the other place). Definitely do as much as you can without branching, but always good to have as an option.
(Another option for "branching" is to switch colors, but for many puzzle types this is actually a bit clunky. In general it doesn't work well with pencil marks, but it's fine for puzzles like Tapa.
The only puzzle where I always use multi-colors is Sternenhimmel (Starry Night). I quickly mark all the possible star locations in red, then mark which places the stars can't be in black, then delete the red...)