How do you make project manager understand that sometimes you can’t give correct estimates for some tasks or bugs?

Hi guys, My question is that when the client releases the requirements for the project, in our company we have to estimate and then give those estimates to the client, if they are happy, they give us a project else look for a different service provider. But how can I give 100% proper estimation when I have never worked on that project, currently there is a project where we have to upgrade Java version of the app, I don't know how many things will break once I do it and the Project manager wants me to estimate it. But I don't know how can I give an estimate to him, what if I give very few days and it turns out many things are breaking, the PM will blame me then for giving poor estimate. He is already trying to go aggressive on timeline so that our company can get the project. How do you folks in service based companies deal with these estimation related issues when you haven't worked on the project because the client will give us contract based on those estimation only. Does the contract become void if we are not able to deliver on those estimates, who takes the blame for these?

1. Over estimating the efforts 2. Office gossips 3. Moon lighting 4. Unrealistic Salary demands 5. Completely under-utilised but still complaining of overwork.

Sometimes PMs want to change the flow of way things working. They often say it's a small change and will not take much time. They see things on high level, but they don't see what are the logics behind need to change and what are DB migration required and sometimes it is not possible to change because many things dependent on it.

My manager, while not technically inclined, oversees an engineering team, making it challenging to update him on intricate scenarios beyond his expertise. He tends to consult his former team, unrelated to our current one, for guidance when he doesn't grasp the situation. Additionally, he organizes meetings with external parties for minor issues, leaving little time for our team to devise solutions. He often proposes numerous ideas that exceed our current bandwidth. His commitments to higher-ups and clients sometimes involve unusual deliverables. While I don't view him negatively, there's a misalignment within our team. How can I navigate this situation?"

There is this new PM who is making my life living hell. Sets up his own timeline without consulting me how much effort it will take me to execute. The requirements are fuzzy and changes while executing. I am having to delete a ton of my code because they can't keep the requirements frozen. The problem is that, I am being pulled into meetings all day and I am having to code at night just to keep up with my tasks. My life has become work and I have no time for my self-care. Haven't gone home in 6 months now. I don't know what to do now. Save me. Please. I beg of you. What should I do?

how do you guys deal with managers setting up unrealistic deadlines? My manager without even consulting the team about efforts required gave the estimated completion date of the project which is impossible to deliver by that time. I tried to reason with him several times about extending the timeline but he doesn't listen at all. what should i do in this case?

So thing is In last 1 week my manager/project lead has been threating that you will have to work on weekend if you dont complete your task by friday and put the the task to testing. And this boils my blood soo damnn much . But as a person who is on lowest level i cant do/say shit. I just disagree with him and dont argue. What would you have done .[ practical advice only] And thing is i do all my dev work on time even earlier almost everytime and he just goes around and threatens everyone with this. Soo annoying thay dumbfk needs to get rekt .

Same as title. As a product manager, what to do when your EM is not supportive and passes the buck to you always, doesn't accept mistakes, instead waits for the chance to blame you instead. You can't even escalate, because of course you have only one EM. Of course, your team's EM will not change.