Streaming problem (NFS/FTP)

Hey everyone, i have a problem with streaming my movies over NFS and FTP.

First of all my setup:

• NAS connected over cable to my switch
• Notebook connected over cable to the switch
• tried with an old HDD and a SSD

I have a movie folder on my hdd, which is shared over nfs and ftp. I can acces it with FileZilla and Kodi. But with some files (mostly files over 10 GB, with a few under 10 GB) i am not able to jump to a specific time. It is not an issue of Kodi, because i already tried opening the FTP Link with VLC media player (which worked) but when i tried to jump (e.g. to 00:01:00) it was loading for a long time, until it played it (like Kodi). I've tried it over wifi and over cable and got the same results (cable didn't take as long as wifi). It is like the movie is being downloaded into a temporary folder in order to play it.
I don't think it has something to do with the network speed, because with some big movies (bigger than 8 GB) i was able to jump (nearly) immediately to the end of the movie and with some small movies (5 GB) it took me ages to jump to any time.

Does anybody else have this problem or is there something wrong with my hardware?

My NAS Build:

• AMD Athlon 5350
• AsRock AM1B-ITX
• Kingston RAM 4 GB

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Hallo Leute, ich habe ein Problem, meine Filme von der NAS auf meinen Laptop/Raspberry zu streamen bzw abzuspielen.

Meine NAS ist über LAN Kabel mit meinem Gigabit Switch verbunden, welcher wiederum über LAN mit meinem Notebook verbunden ist (ich gehe auf den Raspberry nicht ein, da dort das gleiche Problem herrscht).
Wenn ich über Kodi (formerly XBMC) versuche, bei Filmem über NFS oder über FTP zu einer Position zu springen (z.B. ans Ende des Filmes) dauert es bei einigen Filmem (hauptsächlich Filmem über 10 GB und einem 4 GB Film) Ewigkeiten bis es lädt.
Kurz zum Streaming-Verhalten der unterschiedlichen Fälle (beobachtet aus dem Task-Manager):

• Filme über 10 GB und der eine mit 4 GB

• Film fängt an und ladet ein wenig vor
• Ich versuche ans Ende des Filmes zu springen
• "Downloadmeter" im Taskmanager springt hoch und lädt und lädt und lädt
• Annahme: Film wird bis zu der gesprungenen Stelle heruntergeladen

• Filme unter 10 GB

• Film fängt an und ladet ein wenig vor
• Ich versuche ans Ende des Filmes zu springen
• "Downloadmeter" im Taskmanager springt kurz hoch, es lädt ein wenig und der Film wird am Ende des Filmes fortgesetzt.

Oben habe ich meinen NAS-Aufbau hingeschrieben. Hat das etwas mit Openmediavault zu tun, da es über FTP und NFS passiert.

ICh werde mal später Screenshots vom Taskmanager anhängen, damit ihr eine bessere Vorstellung habt.

Vielen Dank im Voraus.

EDIT:
It has nothing to do with Openmediavault:
I've backed up Openmediavault and installed Ubuntu Server and tried the same process with NFS; same result: it won't stream "normally" it is trying to download the file, when trying to jump to another position.
So i'm assuming it has to do with my hardware:/

Old text:
I'm not streaming over FTP. I wanted to be sure, that it's not something NFS specific: i got the same problem on both protocols.
Do you refer with "slow cpu" the cpu of the NAS or the client where the movie is played? I've observed the CPU usage when it was streaming and when i tried to jump forward: It did not past 5%. The network i've tested on (i wanted to be sure, that the network wasn't the problem) is a Gigabit Network. NAS -- Cat5 cable -- Gigabit Switch -- Cat5 cable -- Client (Nas and Client have Gigabit Ports). Just a minute ago i've connected both my android phone and my notebook over nfs to the server and was streaming Full HD Videos and the CPU didn't even reach 5% (Both were now connected over wifi g)
Sorry i forgot to add it into the english part: i've already tried it with my raspberry and got the same result.

Both Raspberry and my Notebook were running Kodi, but like i said, i already tested it with VLC over Raspberry.

In the NFS settings i've increased the number of servers to 16 and these options are activated: subtree_check,insecure.

Thanks in advance