[Rajesh Kumar]

First you can use the File > Reduce Project command by selecting the final composition so that the files that were imported by not used in the project gets removed from the project, after that use the command File>Collect files and make sure that all files option is choosen before you click the Collect file button.
There is a very good video step by step tutorial at https://bluefx.net/after-effects-templates/collect-missing-files-tutorial/ which can refer to in case there is any confusion.

[Rajesh Kumar]

There is a small icon in After effects in the shape of a star that helps you fix the problem you have encountered. Refer to the tutorial https://bluefx.net/after-effects-templates/importing-your-logo-rasterizing/ so that you can fix the problem easily by follwing the simple tutorial.
Thanks

[Rajesh Kumar]

The secret preference option should be helpful when you get this type of error message. You can check one of my other post here which i guess might help you in this regard.
https://forums.creativecow.net/readpost/2/1034602

[Rajesh Kumar]

As others have pointed out without knowing further details it is a bit complicated to explain. I have found a couple of tutorials from https://bluefx.net which might help you in this regards. You can go through some of the tutorials from bluefx.net from the following links and i hope that explains you how you can use After Effects and know more about how to render complex project.

https://bluefx.net/after-effects-templates/ae-setup-max/

https://bluefx.net/after-effects-templates/rendering-in-after-effects-the-effective-way-part-1/

https://bluefx.net/after-effects-templates/rendering-in-after-effects-the-effective-way-part-2/

https://bluefx.net/after-effects-templates/modify-render-preview-heavy-projects-in-after-effects/