Do you think that faith, is just an opinion?

Yes

YES, Of course.

But what is faith? The apostle Paul wrote: “Faith is the assured expectation of things hoped for, the evident demonstration of realities though not beheld.” (Hebrews 11:1) Our faith makes us sure that everything God promises in his Word is as good as done. Faith is also “the evident demonstration,” or evidence for conviction, regarding unseen things. Our mental perception and heart appreciation convince us that such things are real, although we have not seen them.—2 Corinthians 5:7; Ephesians 1:18.

Can you show in any objective way that it is not? The simple answer is yes, faith is an opinion. It is very easy to claim results of faith (i.e. miracles) and that those that do not have faith don't experience them, however, this is confirmation bias i.e. interppeting the data to support your belief (or faith),

Many people have faith in their opinions, but few have objectively verifiable evidence to support them. As an example, look at the new tax plan, the Republicans have faith that it will increase jobs and wages while the Democrats believe that it will not. Hmmm, maybe this is a bad example because the causes and effects are are so subjective that both sides are philosophies rather than science - oh wait, that's the point I'm making, neither side can point to objectively verifiable data that solidly supports their viewpoint.

A different example, and one that I'm sure will disagree with believers in several religions, is that the Bible claims that Christians worship the same god as the Jews and the Quran claims that Muslims also worship the same god, Now the problem is that no matter how firmly a person has faith that their god is the same as believers in the other religion, there is no objective or impartial way to confirm or disprove that faith. I would say that Jews, Christians and Muslims (not to mention Mormons, Bahia and others), all worship different gods, but members of each religion would strongly claim that I was anywhere from completely wrong to being partially right, depending on their faith.

Faith is a synonym for "gullibility".

"I have faith fairies are real" = "Someone said fairies are real and I am so gullible I believed them".

It is an instinct

Faith is complete trust and confidence in something. An opinion is a view or judgement based on something that doesn't necessarily depend on fact or knowledge of it, that's why people have different opinions. For different circumstances some may have faith in something while others don't and that is an opinion looking at it that way. The other way is a feeling.

Faith is something you need in order to believe in Islam. There are ways to increase and reduce faith. Reading Quran, going to the mosque, lowering ones gaze, doing good deeds increase faith. Sinning weakens faith. Disbelievers have zero faith, as they have earned.

An opinion is your interpretation of something.