i know scales but cannot improvisation

i know 
c major and c minor and  harmonic minor  and  a minor pentatonic 

When i play backing track i can't improvisation

I  need  helpe 
Step one - learn some solos  by ear - pick a  really slow solo to start and take it one note at a time.  That's how you get started. You need to do this first and it will make your life infinitely easier going forward when it comes to improvising.  Pick a song in A Minor to start and focus on that key.  Once you've learnt a solo - try playing around with the notes and changing some of the patterns to fit different situations.

Also, on the subject of backing tracks,  make sure at the start that you're practicing over a one-chord vamp - do not try improvising over a backing track with chord changes at the start, it will just confuse you.  Save that for later. 
Do you ever make up any little licks or original patterns with those scales? If you aren't doing that, improvising over chord changes will be tricky because you've learned nothing but how to copy a specific pattern.
Try to improvise in musical 'sentences'; i.e. improvise a simple idea - maybe 4 or 5 notes long. Then, rather than switching to another idea, try to reuse that first idea but vary it in some simple way; e.g. change the rhythm, change a note or two, try it elsewhere the scale. Then reuse it again with another variation, etc...

If you listen to great solos, you will often hear repetition or ideas in this way. It doesn't mean this is the only approach, but it is a good one to get a basic handle on.
I can improvise in pentatonic but really gotta get back to practicing other scales. I used to practice a lot of ascending and descending patterns in triplets or fourths. Unfortunately now when I improvise those patterns are my crutch and I go to them constantly. Just let your mind wonder and "explore" around the fretboard in the right key. Improvising is easy, improvising so everything you play doesn't sound like the same crap is hard. We tend to find note combinations that we like and/or are easy for us to play and it's easy to get stuck there.
Record two chord or tab it in guitar pro

2 bars of C chord
2 bars of G chord

Use C major scale for improvising over it
On the first chord play anything you want from the scale create some phrase - your goal here to stay in the key so don't play wrong notes outside of the C major scale
On the second chord use one of the notes of G chord (G, B, D) to finish your phrase and hold it over G chord, maybe put some vibrato on it

Repeat it a lot of times this is basic of improvisation - finding consonant notes for the phrase's ends and stay in key
You don't need to always do improvisation that way, of course, but it's great to start