It seems to me that

به نظر من می‌رسد

I assume that

گمان می‌کنم که

As far as I know

تا آنجایی که من می‌دانم

I would say that

من می‌گویم که

I believe

من باور دارم

It seems to me that

به نظر من

From my point of view

از دیدگاه من

If you ask me

اگر از من بپرسی