Answer: Here are some synonyms for “I think” .
Explanation: you could possibly use “I believe” or “In my opinion” From my point of view” or “ From were I’m standing” “I presume” “ In my judgement” “In my humble opinion”.
Personally, I strongly* believe (that) ... /deeply / firmly / truly/ completely/
fully/ honestly / genuinely / sincerely.
I’m absolutely* convinced (that) ... / completely / fully / totally / deeply / firmly
I hope these answers complete your sentence!