here i attached one file
the problem is top part(5_1)
my question is how to create the part in good mating condition.
There are a few ways to achieve a perfectly fitting cover for your part. Building on what you've done so far, here is one way to model it, if the design intent is that the top nests down inside, which is how it appears to look in the preview of the assembly (which won't open due to aforementioned reasons).
This method creates a surface 'cutting tool' to carve out a perfectly fitted top.
Step 1: Roll back to just after "clip cut" draft feature.
Step 2: Create 'offset surface' feature on the exterior surfaces that intersect the top edges of the part.
Step 3: Create 'extruded surface' feature 2mm offset inward from the top edges of the part as shown. Extend the sketch segments and extrude width both directions a little beyond the part.
Step 4: Create 'trim surface' feature, with 'mutual' trim type, keeping the yellow portions
Step 5: create a 'split' feature to create the new solid that will be the top cover.
Step 6: create 'move face' feature on the edges of the top cover for assembly clearance if desired.
step 7: there is no step seven, just 'roll to end' and its done.
OOPS! there is a step 7!
Re-define the shell feature to remove original shelled surfaces and add the new surfaces created by the splitting away of the top cover.
Now the part will have 3 bodies, the main part, the battery door cover and the top cover.
Like I said in the beginning, there's more than one way to do this, and more than one place to get it done in the model. This way was a little less elegant than it could have been if modeled differently from the start, but I think it accomplishes what you're looking to do.
The attached part file uses a 'solids only' method that is a little cleaner.