If it's a matter of looking comparable to men in business formal at meetings, I think you should start with a basic plan which is comparable to what men do. I don't know about Austria, but when my husband worked business formal in Boston, MA, and that was about 15 years ago, I can still tell you the 6 suits that he wore to work.
(1) Black with thin bright white pinstripes (2) Black with muted golden brown pinstripes (3) Dark gray with muted white chalk stripes (4) Muted olive green (5) Muted mushroom brown (6) Deep cerulean blue with a very subtle navy plaid overlay. Six was the best way to not look the same for one work week at a time and still have allowances if one of those suits had to get repaired. So my first advice is to find your most essential six which look different from one another, yet are basic enough for adding accessories easily.
This might mean having six tailored, or it might mean buying six new ones. I think that it will depend on whether your existing clothing needs to go down more than one full size or not.
If you are going to buy new ones and budget is tight and you still also might lose more weight, then if it were me, I would unlined bottoms which can coordinate with unlined blazers: also including either boiled wool or thicker sweater-knit blazers. Basically, I am thinking about items which can be further narrowed without having to first undo an inner lining and then put it back again. You will also find this type of item is more forgiving if your weight fluctuates a bit.
Also, two of my quick fixes for times when I don't have the time to restock. I will wear my older bras with added half a cup silicone inserts so as to keep filling out the tops of jackets. I also tend towards chunky shoes and boots, because they make less of a contrast to pants which are a little bit loose.
My biggest tip is that if you can tolerate wearing skirts a lot, skirts are the easiest to camouflage with a sweater on the top or they're cheapest to make smaller around the waist.
Also, I am not loving the pink sweater with this suit. I think that it would be nice with jeans, but the way it bunches around the bottom around your waist seems too casual for a suit, in my opinion.
Personally, I like to make oversized clothing look more deliberate by adding one bolder accessory up top, like an interesting silk scarf or interesting brooch on the jacket or a deep color like cobalt on the blouse. I think that it manages to take the focus away from the looseness and make it seem more like a relaxed vibe than a sloppy one. It also helps if only one piece seems loose. Furthermore, it seems like a lot of the problem is that your clothing is now too long. In the US you can usually find dry cleaners who also shorten sleeves or hems for cheap and don't have the skills for full alterations so they charge much less. If it were me, and such a service is available to you, I'd probably start with just shortening sleeves and pants on two or three suits and not worry about the middle. People notice the length more (because it looks like hand-me-down items) whereas looking like your clothing is a little bit roomier just indicates you have lost weight and doesn't carry such a stigma.
I'd advise against Zara suits and such, because I find that they can shrink even more than the amount which you are loosing weight. And they do this in unpredictable ways. I'd get some trendy blouses or sweaters or accessories there or someplace similar, to liven up the look, if you can find things which are to your taste.