Update wording in ussue template and security reporting

.github/ISSUE_TEMPLATE/BugReport.yml

@@ -150,5 +150,5 @@ body:
     attributes:
       label: Notifications-Menu
       options:
-        - label: I have checked that all checkboxes are ticked under Settings --> Notifications
+        - label: I have checked that all checkmarks are present under Settings --> Notifications
           required: true

SECURITY.md

@@ -2,20 +2,20 @@
 
 ## Reporting a Vulnerability
 
-It is highly appreciated to report a vulnerability to the Monal developers. We ask you for
-disclosure until it has been fixed. This prevents abuse and exploitation in the current published releases.
+It is highly appreciated to report a vulnerability to the Monal developers. We kindly ask you to not
+disclose it until it has been fixed. This prevents abuse and exploitation in the current published releases.
 
-Please report issues directly to [email protected].
+Please report issues directly via mail to [email protected].
 
-Please try to report 
-- in detail what you are concerned about
+Please try to report in detail:
+- what you are concerned about
 - if applicable, how to reproduce
 - your contact details, if the sending email is not enough. That way we can ask questions back to you. 
 
 You are also invited to make a recommendation on how to fix a potential security vulnerability.
 
-Once a vulnerability has been announced and indicated we try our very best to provide a fix as soon as possible,
-at its best within days. However, dependent on the potential issue it can take longer if many code sections need to be changed.
-Please be reminded that this is a non-commercial software project.
+Once a vulnerability has been reported and confirmed we try our very best to provide a fix as soon as possible,
+at its best within days. However, depending on the potential issue it can take longer if many code sections need to be changed.
+Please keep in mind that this is a non-commercial software project run by volunteers.
 
 Thank you for considering to report a security vulnerability. This improves the quality of the app significantly.