is it advisible to use my last 20k to purchase connect on upwork sice it's the minimum
Depends. If you use your last 20k, what of feeding, data, and other life needs? Instead of spending your last kobo on buying Upwork connects which isn't even sure to be enough to get you a job, be patient and wait till you have enough to spare before trying out Upwork again. Once you have enough money, you can then buy Upwork connects and still be able to survive. 20k is even very small. Even if you buy Upwork Connects worth 50k or much more, you can burn through it completely without getting a single job.
So, don't do that. Look for more money - either you find other work you can manage or get money from family and friends. When you are more stable, then you can go all out to conquer Upwork.