Cfrtjryk

I have a layer of polygons that are pretty detailed.

I need these to be more simple.

Is there a way to make this into a polygon with just the outer boundries?

If you're willing to lose some detail in the outer boundary, you can use the buffer tool as follows:

1. 
   

   Measure the widest gap that you want to eliminate. Buffer the polygon by slightly more than 1/2 of that value.

   
   
   

   Eg, if the widest gap is 1 km, buffer the polygon by 0.51 km.
   
   

   
   


2. 
   

   Buffer the result of step one with a negative value of the same magnitude.

   
   
   

   Eg, if the first buffer had a radius of 0.51 km, buffer it by -0.51 km.
   
   

   
   

Now you should have a polygon without the internal gaps, and with a simplified version of the original outer boundary.

Couple ways of doing this:

In the Advanced Digitizing Toolbar you can use the Delete Ring option and manually remove all the gaps.

You can use the v.clean function in the Processing Toolbox which will fill in all the gaps as new polygon features, then you can use Dissolve to merge them all together. Bear in mind I haven't used v.clean before so I don't know what affect it will have on attributes.