好像说话很困难 = it seems talking is difficult 好像连说话都很困难 = it seems even talking is difficult（In the third case） 都 adverb There are four means 1，means all: 都=全部quan bu=whole/all 任何一件事（全部）都应该把它做好。ren he yi jian shi qing dou ying dan ba ta zuo hao. 2，（use after是） just because of: 都是=正因为zheng yin wei=just because of It was all because of your slowly that we were late. 都是（正因为）你太慢， 害得我们迟到了。dou shi ni tai man, hai de wom chi dao le. 3，means: even: lian.... dou He didn't even look at it. 他连看都不看它一眼。ta lian kan dou bu kan ta yi yan. 好像连说话都很困难 = it seems even talking is difficult 4. means: already:=已经 yi jing It's already eight o'clock. Why don't you get a move on? 都（已经）8点了， 你还不走?dou 8 dian le, ni hai bu zhou。

sentance："他病了，好像（连）说话都很困难。” Key grammar："（连）......都+v./adj./vp." adv. It strengthenes the tone and means that “Some situations are unlikely，but it really happened now.”or extreme and abnormal situation 1. strengthenes the tone：他病了，说话很困难 < 他病了，（连）说话都很困难 2.Some situations are unlikely，but it really happened now In normal ，“说话” is an easy thing to do ,BUT it becomes difficult now because he is ill ！ 3.you say "There is only one thing "说话", so why is 都 needed when there is only one thing that is difficult?" in this situation ,"都“is an adverb ，too.BUT it is the another means of"都".It means "All included" "都"is a magic words which has different pronunciation and different parts of speech. DO not worry about it ,as you learn more deeply, you will learn more.

In this sentence, there is a grammar knowledge: 连...都.... which 连 can be omitted. so whole sentence means illness is so serious that he even cant speak.(it you cant understand because of the grammatical errors, just contact me.)

I would answer this question that you ask: why is 都 needed when there is only one thing that is difficult? here is the answer: Isn't talk is easy for you?He is too ...to say a ward.他病了，好像说话都很困难In this sentence,the meaning of 都 isn't both or among...I can't describe it clearly,but you could understand it in this way: 都 in this sentence means even.He is ill,and he even couldn't say a word.This is my answer.Would you mind add me to your friends to learn from each other?If so ,I would be greatful.PS:If you use QQ,my number is 1606251360

In my opinion,althought only one difficult thing in this sentence,Chinese like to feel pity about that not only he got sick, "but" feel pity that he cannot talk easily... "but" in here is same as "都". ..Strictly speaking, the concept of "都“ you think is right,chinese just like to talk with more emotions (like,pity,shock...）it's make it more like oral language. (i am not prefect at English,hope u can understand)