Q:

How to connect contour lines from two different sources?

How to connect contour lines from two different sources (LiDAR & Photogarametry) in order to obtain continuous and uniform contour lines layer ? how can i interpolate them together ? How can i Snap lines only if they have the same Height value ?

A:

Since the distance between the lines in your two data sources can vary greatly (at least it looks like this on the picture), you might need to do some manual work. However, I'd suggest trying the Extend line GP tool (Editing toolbox) or Snap tool (same toolbox). 

This tool extends line segments to the first intersecting feature
  within a specified distance. If no intersecting feature is within the
  specified distance, the line segment will not be extended.

You might also test to use the Load Objects to load features from one source to another and set snapping settings. I use it quite often when "merging" road datasets from different sources and it reduces amount of manual work that will be needed to get done anyway.
There is a great blog post from Esri, where you can get more tips on data processing for such cases. They mention also using Integrate tool, Trim line and some other custom GP tools the Esri Editing team has published.

