Question Cannot implicitly convert type 'string' to 'TMPro.TextMeshProUGUI'

Hello im trying to put a string to a textmeshpro text but this error keeps showing up.

here's my codes:

Code (CSharp):

1.  
2.     [SerializeField]
3.     public TextMeshProUGUI resulttxt;
4.     [SerializeField]
5.     public TextMeshProUGUI explanationtxt;
6.     private string infp;
7.  
8.  
9.     void Start()
10.     {
11.         resulttxt.text = PlayerPrefs.GetString("typeA") + PlayerPrefs.GetString("typeB") + PlayerPrefs.GetString("typeC") + PlayerPrefs.GetString("typeD");
12.         ExplainType();
13.     }
14.  
15.     void ExplainType()
16.     {
17.         if (resulttxt = "INFP")
18.         {
19.             infp = "ate angel ganda";
20.             explanationtxt.text = infp;
21.  
22.         }
23.     }

UI view:

 

if (resulttxt = "INFP")

should be

if (resulttxt.text == "INFP")