No, you can't, and besides, that would be a very bad idea.
That's because when applications (for example, your web browser, Desktop environment, or even the Linux Kernel) get updated, the new version will come with all the changes, some of which may be feature / performance updates, but it will have security fixes too.
For example, when a new version of Firefox comes out (for example, going from Firefox 57 > 58), it will have both new or improved features, and fixes to address security issues. You can't just take the new features while not getting the security changes because they're all part of one thing. Every other part of the system works the same way.
if i am correct i want only those improvement/bug fix updates. i really don't need security updates because my usage is very simple (watching youtube, listening soundcloud, etc)
No, you're not correct. Even with useage like you describe, you almost certainly do want security fixes. There's a lot of malicious things on the internet - for example malicious advertising getting access to data it shouldn't or installing malware, which is possible if there's a security issue found in your browser and you don't update.