I checked the "conclusions" of the first two: https://www.ncbi.nlm.nih.gov/pubmed/29996112 and https://www.ncbi.nlm.nih.gov/pubmed/29709736
Conclusion of 1) Despite the improved exposure assessment approach used in this study, no clear associations were identified. However, the results obtained for recent exposure to RF electric and magnetic fields are suggestive of a potential role in brain tumor promotion/progression and should be further investigated.
Conclusion of 2) Ever use of wireless phones was not significantly associated with risk of adult glioma, but there could be increased risk in long-term users.
They both read as, "we found no significant effect".