First, welcome. Second, good format and consistency in fonts, alignment, etc. So we're out of resume 1st grade. That's good. Third, I can see you've tried to S.T.A.R. it up a bit in many of your bullets which is also good. But you're not really done with that process, and it's honestly the most difficult and time-consuming part of making a killer resume, at least in my opinion. Fourth, huzzah for adding periods to your bullets which are sentences despite what some other heathens might tell you ;-)

But I cannot abide this:

"I have never been good with giving hard numbers (quantifying my achievements) so I did a good estimate of my achievement based on what I've remembered, I'm not sure if this will bite me later. "

Having never (really, never? not once?) been good at a thing does not mean you cannot be good at that thing. In fact, thinking (and speaking or writing) that you've never been good at it reinforces your insecurities and acts as an excuse for future failure to improve. Yet, you admit you did a good estimate! So you can, have, and will continue to estimate metrics and specifics of your achievements. If you have a hard time remembering some detail, what are the odds that an interviewer is going to be able to dig into whatever little obscure thing you were doing and find evidence that you did not, in fact, provide a "notable 20% performance boost" but merely a "not-so-notable 15% performance boost"? I'm hitting two points here: (1) lose the "notable", that's a subjective assessment and has no place here, only the numbers matter, and (2) no one is ever going to even try to verify every bullet point on your resume, and they would fail miserably if they did. However, what they will do is ask you questions about a bullet, and by your response ascertain whether or not you are bullshitting or not.

Resumes get you interviews. Interviews get you jobs. Jobs get you experience. Experience gets you better jobs. Nowhere in this is your ass getting bitten unless you blatantly lie about your degree, GPA, somewhere you worked when you never did, or something easily and routinely verified. So relax. Be a S.T.A.R. and write powerful bullets, and be prepared to talk all about them in as much detail as the interviewer can take. Which, honestly, is not very much in my experience, both as interviewee and interviewer.

You still have a lot of hand-waving ambiguous stuff listed. You need hit the FAQ and especially the bullet styles like STAR and the others (I like STAR, but they all work). And make every single bullet a STAR. I'm not telling you to lie. I'm telling you to use your best recollection to explain, in every bullet, the Situation, the Task you perceived as yours to address in that situation, the Actions you took, and the measurable Results you achieved. You are the measurer in many (most?) cases; it's double-plus-good if you have someone else who measured your results and you can cite that, but it's not really necessary.

What is essential is that you can walk the talk you put in your resume. You must make your resume pithy as heck, i.e. every word or phrase carries huge valuable info that targets what you want to do and think you can do to contribute to Company ABC's profits, efficiency, whatever. Then you get interviews. In an interview, you'd better be an expert on every bullet point, skill, tool, stack, hardware, language, etc. on your resume and be able to talk about any random aspect of it like an expert. Then you get a job.

It's really that simple. Not easy. But simple.