You can't add two character arrays together and get a meaningful result. They're pointers, not a class like std::string which provides such useful operations.
Create a large enough TCHAR array and use GetTempPath, then use strcat to add the file name to it.
TCHAR temp_file [265];
GetTempPath(255, temp_file);
strcat(temp_file, "temp1.txt");
Ideally, you should also test the result of GetTempPath for failure. As far as I can see from the documentation linked in the other answer, the most likely reason for failure is that the path variable supplied is too small. Use MAX_PATH+1+9 as recommended there.