Most likely you should fix the data importing, rather than messing around with converting strings.
load('data.mat')
T = varfun(@str2double,A_NFC);
T.Properties.VariableNames = A_NFC.Properties.VariableNames;
T.Time = datetime(A_NFC.Time,'InputFormat','dd.MM.yyyy')
T = 290×14 table
Time OTH_MFI_PLN OTH_MFI_FX OTH_MFI_TOT OTH_MFI_LOANS_PLN OTH_MFI_LOANS_FX OTH_MFI_LOANS_TOT OTH_C_PLN OTH_C_FX OTH_C_TOT MFI_L_C_PLN MFI_L_C_FX MFI_L_C_TOT ACC_INT
___________ ___________ __________ ___________ _________________ ________________ _________________ _________ ________ _________ ___________ __________ ___________ _______
31-Jan-1997 45912 9617.1 55529 44099 9473.4 53572 1813.4 143.74 1957.2 45947 9617.1 55565 4795.2
28-Feb-1997 46740 9847.3 56588 44820 9698.6 54519 1919.8 148.64 2068.5 46775 9847.3 56623 5139.7
31-Mar-1997 47462 10511 57974 45483 10347 55829 1979.8 164.6 2144.4 47497 10511 58009 5203.3
30-Apr-1997 47953 11039 58991 45924 10861 56784 2029.3 178.14 2207.4 47988 11039 59026 5166.8
31-May-1997 47994 11559 59553 45932 11386 57318 2062.5 172.26 2234.7 48029 11559 59587 5474
30-Jun-1997 48616 12178 60794 46465 12003 58468 2150.2 175.7 2325.9 48655 12178 60833 5492.2
31-Jul-1997 48879 12955 61834 46705 12776 59481 2174.2 178.85 2353.1 48918 12955 61873 5643.3
31-Aug-1997 50083 13308 63392 47864 13117 60980 2219.7 191.61 2411.3 50123 13308 63431 5871.7
30-Sep-1997 51687 13711 65398 49435 13493 62928 2252 218.73 2470.7 51723 13711 65435 5747
31-Oct-1997 52222 14479 66701 49914 14245 64160 2307.7 233.32 2541.1 52258 14479 66737 5684
30-Nov-1997 54814 14603 69417 52447 14382 66828 2366.9 221.2 2588.1 54850 14603 69453 6004.4
31-Dec-1997 55057 14206 69264 52790 13990 66780 2266.9 216.65 2483.6 55096 14206 69303 4710.6
31-Jan-1998 57150 14898 72048 54852 14680 69532 2298.3 217.63 2515.9 57189 14898 72087 4788.8
28-Feb-1998 57817 15194 73011 55525 14970 70494 2292.4 224.58 2517 57856 15194 73050 5051.2
31-Mar-1998 58541 15563 74104 56157 15344 71501 2383.6 218.96 2602.5 58580 15563 74143 4922
30-Apr-1998 58547 16710 75257 56121 16475 72596 2425.6 234.78 2660.4 58586 16710 75296 4809.1