Accessing Object Properties Dynamically

You can do it like blow assuming that map contains key values as string pair of object field name and value

        Map<String, Schema.SObjectType> descMap = Schema.getGlobalDescribe();
        Schema.SObjectType leadSchema = descMap.get(objectName);
        Map<String, Schema.SObjectField> fieldMap = leadSchema.getDescribe().fields.getMap();
        // objectRecord is the object of any custom or standard object
        // recordMap is the map of <String, String> 
        for (String sfdcFieldName: recordMap.keySet()) {
            String fieldValue = recordMap.get(sfdcFieldName);
            Schema.DisplayType fieldDataType = fieldMap.get(sfdcFieldName).getDescribe().getType();
            if (String.isNotBlank(fieldValue)) { // this is just to make sure we are not setting blank. if you need to set blank then remove this check.
                if (String.valueOf(fieldDataType).equalsIgnoreCase('boolean')) {
                    objectRecord.put(sfdcFieldName, Boolean.valueOf(fieldValue.toLowerCase()));
                }
                else if(String.valueOf(fieldDataType).equalsIgnoreCase('decimal') || 
                    String.valueOf(fieldDataType).equalsIgnoreCase('currency') || 
                    String.valueOf(fieldDataType).equalsIgnoreCase('double') ||
                    String.valueOf(fieldDataType).equalsIgnoreCase('percent')) {
                        objectRecord.put(sfdcFieldName, Decimal.valueOf(fieldValue.toLowerCase()));
                }
                else if(String.valueOf(fieldDataType).equalsIgnoreCase('date'))) {
                        objectRecord.put(sfdcFieldName, Date.valueOf(fieldValue));
                }
                else if(String.valueOf(fieldDataType).equalsIgnoreCase('datetime'))) {
                        objectRecord.put(sfdcFieldName, Datetime.valueOf(fieldValue));
                }
                else {
                    objectRecord.put(sfdcFieldName, fieldValue);
                }
            }
        }