By far not the best way, but I've tried to do it without regex:

!/bin/python3

import math import os import random import re import sys

first_multiple_input = input().rstrip().split()

n = int(first_multiple_input[0])

m = int(first_multiple_input[1])

matrix = []

for _ in range(n): matrix_item = input() matrix.append(matrix_item)

string = ""

for j in range(m): for i in range(n): string += matrix[i][j]

symb = ('!','@','#','$','%','&', ' ')

temp_list = []

for idx, c in enumerate(string): ((c in symb) == True and ((idx-1>=0 and string[idx-1] not in symb) == True or temp_list != [])) and temp_list.append(idx)

try: item = temp_list[-1] == len(string)-1 and temp_list[-1] or -999

while True:
    try:
        temp_list.remove(item)
        item-=1
    except Exception:
        break

remove = []

c = 0
while True:
    try:  
        (temp_list[c+1] == temp_list[c]+1) and remove.append(string[temp_list[c]])
        (temp_list[c+1] != temp_list[c]+1) and remove.append(string[temp_list[c]] + "_")        
        c+=1
    except Exception:
        (temp_list[c] == temp_list[c-1]+1) and remove.append(string[temp_list[c]])
        (temp_list[c] != temp_list[c-1]+1) and remove.append(string[temp_list[c]] + "_")
        break

remove = "".join(remove)
remove = remove.split("_")

for c in remove:
    string = string.replace(c, " ", 1)

print(string)

except Exception: # In case the themp_list is [], so we just return the original string print(string)