could we accidently threaten other lifeforms or vice versa?what do you think?

Sure can, I can't wait to shake the hand of an alien after a good sneeze.

Well, whenever the time comes when we set foot on a world teeming with life like ours, that first step may squash a few alien ants or equivalent.
Yes, I could see us unknowingly threaten an alien life form.
I can see that happen especially if the life form is something other than carbon based.

Most people believe that native americans were scattered un organized hunter gatherers. Cortez brought a myriad of European diseases to the americas where the previously unexposed population had no built up immmunities. Measles was fatal.

By the time settlers started moving into and across the Americas what they encountered were the remnants of a once mighty culture decimated by disease run amok.

Yeah, simple organisms introduced into previously unexposed biosystems can have unpredictable results. Many examples of that on Islands and in water systems.

Remember that viruses, bacteria etc are also products of evolution. The odds that a virus or equivalent found on a planet in another solar system being able to contaminate US is essentially zero.

But there are presumably, if there is life out there, a myriad of other risks... Imagine you come across something equivalent to plant life..but one that has found it beneficial to use electricity (a la electric eels) to gather prey ( a la the venus flytrap).. I mean.. really there could be anything..

If a plant could attack you for food so could a bacterium. There are many bacteria that eat only the carbon from crap. They ignore dna and protein present. Dont think they would consider that your dna doesnt look like any other in experiance.

How life might form dna or protein might be different. However the molecules would be the same everywhere. Some sponges in antartica largly silicates or glass but they still eat protein. Microbes at hydrothermal events feed on hydrogen sulfides, but huge colony of life around vents feeding on microbes for energy.

Something might poison itself and die feeding on you, but would still be a threat to you in the attempt. Approach alien biology with caution. For their sake and yours.

Until we encounter the first alien biological environment for evaluation, its all an uknown.