Excel keeps calculating % very slow in a big database

80K rows and 20 columns could choke some computers.
Without much more detail, an answer can't really be given to solve your problem. In addition to attaching a workbook representative of your data (complete with all formulae) a description of your computer would be useful.

Attach a sample workbook. Make sure there is just enough data to demonstrate your need. Include a BEFORE sheet and an AFTER sheet in the workbook if needed to show the process you're trying to complete or automate. Make sure your desired results are shown, mock them up manually if necessary.

Remember to desensitize the data.

Click on GO ADVANCED and then scroll down to Manage Attachments to open the upload window.

Instead of filtering using many formulae, try using the Data, Filter and on column B filter using the Search as shown in the example image. The results are almost instantaneous and don't require formulae.
Filter.jpg

You can also use the TEXT FILTER and enter for peinture the search term *peinture* and the results will be in the same order as the list (unsorted)

If you need to have the results in a printable form, select all the data filtered then go to Find and Select, Go to Special, Visible Cells Only, OK, Copy, go to the destination (another worksheet) and Paste. Partial results are shown below.

	A	B	C	D	E
1	ITEMNO	ITEMDESC	Tariff	Description	Supplier
2	0005875	BAC A PEINTURE TRANS/RLX 180	39269090	PLASTIC GOODS	NESPOLI FRANCE
3	0005858	BAC A PEINTURE TRANS/RLX 110	39269090	PLASTIC GOODS	NESPOLI FRANCE
4	0005942	BAC A PEINTURE NOIR/RLX 230	39269090	PLASTIC GOODS	NESPOLI FRANCE
5	0005932	SEAU A PEINTURE 8,5 LITRES	39269090	PLASTIC GOODS	NESPOLI FRANCE
6	0028271	SEAU A PEINTURE 8,5 LITRES	39269090	PLASTIC GOODS	NESPOLI FRANCE
7	0028272	SEAU A PEINTURE 13 LITRES	39269090	PLASTIC GOODS	NESPOLI FRANCE
8	0028271	SEAU A PEINTURE 8,5 LITRES	39269090	PLASTIC GOODS	FRANPIN S.A
9	0028272	SEAU A PEINTURE 13 LITRES	39269090	PLASTIC GOODS	FRANPIN S.A
10	0028273	BAC A PEINTURE BLEU / RLX 180	39269090	PLASTIC GOODS	FRANPIN S.A
11	0005875	BAC A PEINTURE TRANS/RLX 180	39269090	PLASTIC GOODS	FRANPIN S.A
12	0005858	BAC A PEINTURE TRANS/RLX 110	39269090	PLASTIC GOODS	FRANPIN S.A
13	0005942	BAC A PEINTURE NOIR/RLX 230	39269090	PLASTIC GOODS	FRANPIN S.A
14	0005932	SEAU A PEINTURE 8,5 LITRES	39269090	PLASTIC GOODS	FRANPIN S.A
15	0028271	SEAU A PEINTURE 8,5 LITRES	39269090	PLASTIC GOODS	FRANPIN S.A

This is very quick in comparison to using formulae and there are no formulae that can get messed up.

If you want to use formulae and really speed up the processing, insert a helper column (F) and enter this formula and fill down

Formula:

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Then in I5 enter this array formula and fill down and across

Formula:

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My tests show this combination to be 8 to 9 times faster than the previous formula.