Shorter imported clip than original and so much lag

Hello,

I have two serious problems with my Premier pro 12.1 (last update, trial version). My PC configuration is: CPU Intel i7 5820K 3.3ghz, MB Gygabyte X99 UD7, DDR4 16 GB 1200Mhz, GPU Nvidia GTX 960  CUDA cores 1024, SSD Intel, windows 8.1

1. I have some clips from my Panasonic gh4 ( .mov 25fps, 1920 x 1080, square pixel, audio 48kHz 16 bit, bitrate 50Mb/s) and no matter what importing method I use, two clips of 8 are imported in the premier project as 59 seconds and 1min30s. I use the MPE cuda option in the project settings. Changing to MPE software do nothing regarding my problem. Why this crazy bug happens to my configuration? VLC plays these two videos at the normal length, but premiere pro recognise only a short part of them.The duration for others clips like this, is shows well in Premiere.

I want to underline that any import of a 6-8 mins. full hd video, results in a freezing Premiere with the message" Not Responding". So I must wait 5 minutes just for importing one clip and leave Premier to returns to life.

2. Like you can see, I have a good configuration for editing full hd but I have some serious lag problems so far. When I play a 6-8mins. clip  in source screen of Premiere the image freezes when I jump from a second to another second and the clip never plays from the selected point. If I create a proxy, Premiere converts a clip in 4 minutes...  I understand some kinds of problems for 4k files , but for full hd?! There is a link with the problem no.1?

So, my problems are normal for the clip properties and pc configuration provided? If my hardware is to old, I accept, but in task manager Adobe Premiere stays at 16% cpu and memory consumption, when a video is imported or the image frezzes...

What can I do to solve the problems and convince me to buy the full version, after this trial?