Problems with my NG telescope

[Eoin Fox]

Hi guys, I'm new to the Astro World! I got a National Geographic 76/700;in February and all excited put it together  and found I couldn't use it cos of clouding, Ireland is more cloudy than clear!! Anyways when I was setting it up I accidental ( in my excitement) removed the main mirror at the back.. ( not sure the technical name for it!). I think I may have misaligned the mirror. Is there a way to fix this? The screw head on One of the screws I removed is worn from this ! Well I put it back on and it's catching images but the alignment seems of with the eyepiece.. also a few clear nights now and I've had a good use of it catching some lovely visions of the moon , tried photographing these views but it's not happening for me a lot of glare.. any tips?.. The lenses I have are 9mm, 12.5mm and 25mm. A Barlow × 3 extender and an erecting eyepiece X 1.5. What's the best mix for images...