Hi Ehsan, You can say: “Thank you very much for the invitation to interview for the (job position). I appreciate the opportunity and I look forward to meeting with (Hiring Manager) on (date) at (time) in your (location) office" https://www.paxus.com.au/blog/respond-electronically-invite-interview/

"With your discretion, I declare my readiness for an online interview" is a little bit too intense, the word declare isn't really the most applicable here, it is too emphatic. Try something like, "I welcome the opportunity to present myself for an online interview at your convenience" :)