Considering you have provided
written evidence for measuring performance between yours and LINQ and that your question starts with
"What can I improve" and ends with
"What exactly is better" gives the impression you are seeking help with code code-optimisation or at least code review. Both of which if so are sadly off-topic for SO. It
may be better suited for another SE site but be sure to read the relevant FAQ; and/or re-wording your question as necessary before cross-posting.
How to Ask. Good luck! —
MickyD 7 secs ago