While you are waiting for answers I can share my limited knowledge.

Hormones are often converted to other types of hormones.

"Should it happen, or is there a way we can stop it?"

I do believe men need a small amount of estrogen, but with all the pollution going on and additives in our food hormones can easily get out of balance.

There are things that can help if you suspect you have too much estrogen.  You can look up herbs that block estrogen and see what you come up.  I read that Rosemary can block certain kinds of estrogen.

Spearmint can block testosterone.  I tried drinking a bunch of that tea once to see if it would help stop the robust peach fuzz growing on my upper lip.  It was becoming more than peach fuzz. LOL.  After a few days of drinking lots of spearmint tea I realized it was making me depressed and I decided it wasn't worth it.  Even women need a little bit of testosterone.  And while I wouldn't want to take it purposely I see that it is necessary in giving me energy, libido and a good mood.  Too much though I think can make you feel angry.

You have to be really careful in altering the body's delicate balance.  In my opinion I think a person should judge whether or not something is helping them by how they feel.  If something helps you feel better, that's awesome.  If something makes you feel worse then you should probably stop taking it.

 I read that testosterone in men can become estrogen? I.e. its converted from testosterone into estrogen?

Yes, estrogen is formed in both and women from testosterone through the action of the enzyme aromatase.

Why does it do that, or why do we need that to happen?

Because both sexes have receptors, such as those in bones, that respond to estrogen.  Both sexes also have responses to testosterone, such as maintaining muscle mass as sexua| stimulation.   Also keep in mind what would happen if we only had single hormones without antagonization.  For example, if women only produced estrogen but did not produce testosterone to keep it in check. These hormones can cause various problems if left unopposed such as cancers, weigh gain, hypothyroidism, blood sugar problems, enlarge prostate, etc.

How does that happen? Dont we make estrogen (men) by itself, i.e. is the only way we get estrogen via testosterone?

Yes.

What converts testosterone into estrogen?

Aromatase.

Should it happen, or is there a way we can stop it?

There are ways to reduce the conversion such as nettle root, which is a natural aromatase inhibitor.  You do not want to completely block it though.

What issues in testosterone becoming estrogen could lead to high estrogen levels? I.e. could to much testosterone mean that youll get to much esotrgen as all the testosterone ultimately becomes estrogen?

Not really.  The amount of testosterone that converts in to estrogen is dependent on aromatase activity.  The higher the activity the the more testosterone is converted in to estrogen.