I just read you had only 5 months lessons. Is it? Maybe I've misunderstood but if this is the case I think this be too much of a struggle for you. If you want to start Mendelssohn people normally start with something like this. https://www.youtube.com/watch?v=4p-lnBD4uhMhttps://www.youtube.com/watch?v=5RJ9vHBZIFs
op 117 seems an odd piece to play for the first Mendlessohn. Why did your teacher suggest this so early? I've had almost 15 years of lessons so this I think would explain the difference in what we find difficult. In my experience the faster Mendelssohn pieces are very much harder than the slow. I have only more recently got the dexterity to play some of the faster ones.. Hope I havent put you off but just intrigued by the choice.
The rhythm is indeed another difficult component of this piece. I'm now able to play the first few measures very slow but approaching it less from the mindset of matching up the bass and treble notes and more so in sound patterns.
Regarding the difficulty of the piece for my stage, I can understand how it seems pretty early and agree to a certain extent. My instructor has been very aggressive with progression since the first time I met him. I had been playing one month when I had my first lesson and he gave me Mozarts Sonata Facile k545 (on top of two handed/two octave scales/arpeggios for eminor! for that weeks practice).
We have maintained this very aggressive practice regiment and while I don't have the cleanest most polished pieces once completed, my development has come along quite fast. I now have a few Chopin Waltzes and Mazurkas under my belt and am feeling more comfortable with difficult material.
I am now learning two pieces at a time, a one month piece and a more difficult three month piece. Albumblatt 117 is my three month piece so I'm going to take my time learning it.
I really like how he approaches development as learning pieces outside of your skill range force you to develop certain technique very fast. My left handed arpeggios and ability to make large jumps will be much better because of grinding this piece out.
I initially approached him with two mendelssohn pieces, songs without words no.2 in f minor or albumblatt 117. Songs without words no.2 was a bit too difficult so we decided on albumblatt.
I'm just going to spend the next two weeks or so about an hour a day on simply handling the left hand and slowly incorporate the easy right hand.