What to include in Abstract and Conclusion (and what not to include) of article
What exactly goes into the abstract depends on your field / research problem. It is helpful to remember when the abstract/conclusion is read and what purpose it should fulfill.

The abstract is normally read before the actual paper and the reader needs to decide whether or not the paper is interesting to them and if it worth to invest the time reading it. Therefore, it should include


the problem that was tackled (maybe with a motivation for that problem)
the methods used
what makes the paper stand out from similar work
what kind of results you got


The conclusion is read in the end and should sum up what you want the reader to remember about your work. A motivation is probably not necessary because they took the time to read (most of) your work so it is unlikely they were not interested. The content is similar to the abstract but more focused on the results.


the problem that was solved
the methods used
what makes the paper stand out from similar work
a more in-depth description of the results
limitations
future work